Abstract:
Audio video synchronization and alignment or alignment of audio to some other external clock are rendered more effective or easier by treating fragment grid and frame grid as independent values, but, nevertheless, for each fragment the frame grid is aligned to the respective fragment&#39;s beginning. A compression effectiveness lost may be kept low when appropriately selecting the fragment size. On the other hand, the alignment of the frame grid with respect to the fragments&#39; beginnings allows for an easy and fragment-synchronized way of handling the fragments in connection with, for example, parallel audio video streaming, bitrate adaptive streaming or the like.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of copending International Application No. PCT/EP2016/054916, filed Mar. 8, 2016, which claims priority from European Application No. EP 15158317.6, filed Mar. 9, 2015, which are each incorporated herein in its entirety by this reference thereto. 
         [0002]    The present application is concerned with an audio codec suitable, for example, for usage in parallel to coded video. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    When delivering audio and video content over a transmission channel with either fixed or variable bit rate, one goal is to ensure audio video synchronization and the enablement of advanced use-cases such as splicing. 
         [0004]    Audio and video synchronization and alignment has been a crucial part when building audio video systems. Normally, audio and video codecs are not using the same frame duration. Due to this reason, today&#39;s audio codecs are not frame aligned. As an example, this is also true for the widely used AAC-family. The example is based on the DVB standard, where a 1024 frame size and a sampling frequency of 48 kHz are used. This leads to audio frames with a duration of 
         [0000]    
       
         
           
             
               
                 1024 
                  
                 
                     
                 
                  
                 samples 
               
               
                 43000 
                  
                 
                     
                 
                  
                 Hz 
               
             
             ≈ 
             
               0.0213 
                
               
                   
               
                
               
                 sec 
                 . 
               
             
           
         
       
     
         [0000]    In contrast the common DVB refresh rate for video is either 25 Hz or 50 Hz, which leads to video frame durations of 0.02 sec or 0.04 sec respectively. 
         [0005]    Especially when changing the configuration of the audio stream or changing the program, the video and audio need to be aligned again. Today&#39;s systems will change the audio configuration slightly before or after the corresponding video because human beings are not able to recognize small differences in audio and video synchronization. 
         [0006]    Unfortunately this increases the complexity of splicing where a national advertisement gets replaced by a local one, since the replaced video stream has to begin also with this small offset. In addition new standards are asking for a more accurate video and audio synchronization to improve the overall user experience. 
         [0007]    Therefore recent audio codecs can deal with a wide range of possible frame sizes to match the video frame size. The problem here is that this—besides solving the alignment problem—has a big impact of coding efficiency and performance. 
         [0008]    Streaming in broadcast environments imposes special problems. 
         [0009]    Recent developments have shown that “adaptive” streaming is considered as a transport layer even for linear broadcast. To match all requirements which are slightly different for over the top application and over the air application adaptive streaming has been optimized. Here we will focus on one concrete adaptive streaming technology but all given examples will also work for other file-based technologies like MMT. 
         [0010]      FIG. 7  shows a proposal for the ATSC 3.0 standard which is currently under development. In this proposal, an optimized version of MPEG-DASH is considered to be used over a fixed rate broadcast channel. Since DASH was designed for a variable rate, unicast channel, like LTE, 3G or broadband Internet, some adjustments were needed which are covered by the proposal. The main difference to the regular DASH use-case is that the receiver of a broadcast channel has no backchannel and receives a unicast. Normally the client can extract the location of the initialization segment after receiving and parsing of the MPD. After that the client is able to decode one segment after the other or can seek to a given timestamp. As shown in the above figure, in a broadcast environment this approach is not possible at all. Instead the MPD and the initialization segment(s) is/are repeated on a regular basis. The receiver is then able to tune-in as soon as it receives the MPD and all needed initialization segments. 
         [0011]    This involves a tradeoff between short tune-in time and small overhead. For a regular broadcaster a segment length of approx. 1 second seems to be feasible. This means that between two MPDs there is one audio and one video segment (if the program contains only audio and video) both with a length of approx. one second. 
         [0012]    For audio and video alignment the former mentioned aspect is also true when using DASH. In addition audio segments have to be slightly longer or shorter to keep audio and video alignment. This is shown in  FIG. 8 . 
         [0013]    If an audio or video configuration change is triggered. This change has to happen at a segment boundary, since there is no other way to transmit an updated initialization segment. For that, video and audio are padded (with either black frames or silence) to fill a full segment. But this doesn&#39;t solve the issue of misalignment of video and audio. For splicing and program changes, there can be a small audio and video mismatch depending on the current segment duration drift. 
       SUMMARY 
       [0014]    According to an embodiment, an encoder for encoding audio content into an encoded data stream may have: an encoding stage configured to encode the audio content in units of audio frames; and a fragment provider configured to provide the audio content to the encoding stage in units of temporal fragments by providing, for a currently provided temporal fragment, a portion of the audio content to the encoding stage which includes the currently provided temporal fragment, wherein the encoder is configured to encode each temporal fragment into an encoded representation of the respective temporal fragment in units of audio frames, and the fragment provider is configured to provide the audio content to the encoding stage such that the audio frames are aligned to the respective temporal fragment such that for each temporal fragment a beginning of a first audio frame and a beginning of the respective temporal fragment coincide, and wherein the encoded representations of the temporal fragments are included in the encoded data stream, and a temporal length of the temporal fragments is a non-integer multiple of a temporal length of the audio frames, wherein the encoder is configured to signal within the encoded data stream a truncation information for identifying a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment of the fragment grid, wherein the truncation information includes a frame length value indicating the temporal length of the audio frames and a fragment length value indicating the temporal length of the temporal fragments and/or a truncation length value indicating a temporal length of a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment, or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame. 
         [0015]    According to another embodiment, a decoder for decoding audio content from an encoded data stream may have: an input interface configured to receive encoded representations of temporal fragments of the audio content, each of which has encoded thereinto a respective temporal fragment in units of audio frames temporally aligned to a beginning of the respective temporal fragment so that the beginning of the respective temporal fragment coincides with a beginning of a first audio frame of the audio frames; a decoding stage configured to decode reconstructed versions of the temporal fragments of the audio content from the encoded representations of the temporal fragments; and a joiner configured to join, for playout, the reconstructed versions of the temporal fragments of the audio content together, wherein a temporal length between fragment boundaries of the fragment grid is a non-integer multiple of a temporal length of the audio frames, wherein the joiner is configured to truncate the reconstructed version of a predetermined temporal fragment at a portion of a trailing audio frame of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, which temporally exceeds a trailing end of the predetermined temporal fragment and temporally overlaps with a reconstructed version of an immediately succeeding temporal fragment, wherein the decoder is configured to determine the portion of the trailing audio frame on the basis of truncation information in the encoded data stream, wherein the truncation information includes a frame length value indicating a temporal length of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, and a fragment length value indicating a temporal length of the predetermined temporal fragment from the beginning of the reconstructed version of the predetermined fragment to the fragment boundary with which the beginning of the reconstructed version of the succeeding temporal fragment coincides, and/or a truncation length value indicating a temporal length of the portion of the trailing audio frame or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame. 
         [0016]    According to another embodiment, a method for encoding audio content into an encoded data stream, using an encoding stage configured to encode the audio content in units of frames, may have the steps of: providing the audio content to the encoding stage in units of temporal fragments by providing, for a currently provided temporal fragment, a portion of the audio content to the encoding stage which includes the currently provided temporal fragment, encoding, performed by the encoding stage, each temporal fragment into an encoded representation of the respective temporal fragment in units of audio frames, wherein the audio content is provided to the encoding stage such that the audio frames are aligned to the respective temporal fragment such that for each temporal fragment a beginning of first audio frame of the audio frames in units of which the respective temporal fragment is encoded into the encoded representation of the respective temporal fragment and a beginning of the respective temporal fragment coincide, wherein the encoded representations of the temporal fragments are included in the encoded data stream, and a temporal length of the temporal fragments is a non-integer multiple of a temporal length of the frames, wherein the method includes signaling within the encoded data stream a truncation information for identifying a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment of the fragment grid, wherein the truncation information includes a frame length value indicating the temporal length of the audio frames and a fragment length value indicating the temporal length of the temporal fragments and/or a truncation length value indicating a temporal length of a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment of the fragment grid, or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame. 
         [0017]    According to another embodiment, a method for decoding audio content in units of temporal fragments of a fragment grid from an encoded data stream may have the steps of: receiving encoded representations of temporal fragments of the audio content, each of which has encoded thereinto a respective temporal fragment in units of audio frames temporally aligned to a beginning of the respective temporal fragment so that the beginning of the respective temporal fragment coincides with a beginning of a first audio frame of the audio frames; decode reconstructed versions of the temporal fragments of the audio content from the encoded representations of the temporal fragments; and joining, for playout, the reconstructed versions of the temporal fragments of the audio content together, wherein a temporal length between fragment boundaries of the fragment grid is a non-integer multiple of a temporal length of the audio frames, wherein the joining includes truncating the reconstructed version of a predetermined temporal fragment at a portion of a trailing audio frame of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, which temporally exceeds a trailing end of the predetermined temporal fragment and temporally overlaps with a reconstructed version of an immediately succeeding temporal fragment, wherein the method further includes determining the portion of the trailing audio frame on the basis of truncation information in the encoded data stream, wherein the truncation information includes a frame length value indicating a temporal length of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, and a fragment length value indicating a temporal length of the predetermined temporal fragment from the beginning of the reconstructed version of the predetermined fragment to the fragment boundary with which the beginning of the reconstructed version of the succeeding temporal fragment coincides, and/or a truncation length value indicating a temporal length of the portion of the trailing audio frame or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame. 
         [0018]    Another embodiment may have a non-transitory digital storage medium having a computer program stored thereon to perform the method for encoding audio content into an encoded data stream, using an encoding stage configured to encode the audio content in units of frames, the method having the steps of: providing the audio content to the encoding stage in units of temporal fragments by providing, for a currently provided temporal fragment, a portion of the audio content to the encoding stage which includes the currently provided temporal fragment, encoding, performed by the encoding stage, each temporal fragment into an encoded representation of the respective temporal fragment in units of audio frames, wherein the audio content is provided to the encoding stage such that the audio frames are aligned to the respective temporal fragment such that for each temporal fragment a beginning of first audio frame of the audio frames in units of which the respective temporal fragment is encoded into the encoded representation of the respective temporal fragment and a beginning of the respective temporal fragment coincide, wherein the encoded representations of the temporal fragments are included in the encoded data stream, and a temporal length of the temporal fragments is a non-integer multiple of a temporal length of the frames, wherein the method includes signaling within the encoded data stream a truncation information for identifying a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment of the fragment grid, wherein the truncation information includes a frame length value indicating the temporal length of the audio frames and a fragment length value indicating the temporal length of the temporal fragments and/or a truncation length value indicating a temporal length of a portion of a trailing audio frame of the audio frames in units of which the temporal fragments are encoded, which exceeds a trailing end of the temporal fragments and temporally overlaps with a immediately succeeding temporal fragment of the fragment grid, or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame, when said computer program is run by a computer. 
         [0019]    Another embodiment may have a non-transitory digital storage medium having a computer program stored thereon to perform the method for decoding audio content in units of temporal fragments of a fragment grid from an encoded data stream, the method having the steps of: receiving encoded representations of temporal fragments of the audio content, each of which has encoded thereinto a respective temporal fragment in units of audio frames temporally aligned to a beginning of the respective temporal fragment so that the beginning of the respective temporal fragment coincides with a beginning of a first audio frame of the audio frames; decode reconstructed versions of the temporal fragments of the audio content from the encoded representations of the temporal fragments; and joining, for playout, the reconstructed versions of the temporal fragments of the audio content together, wherein a temporal length between fragment boundaries of the fragment grid is a non-integer multiple of a temporal length of the audio frames, wherein the joining includes truncating the reconstructed version of a predetermined temporal fragment at a portion of a trailing audio frame of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, which temporally exceeds a trailing end of the predetermined temporal fragment and temporally overlaps with a reconstructed version of an immediately succeeding temporal fragment, wherein the method further includes determining the portion of the trailing audio frame on the basis of truncation information in the encoded data stream, wherein the truncation information includes a frame length value indicating a temporal length of the audio frames in units of which the predetermined temporal fragment is coded into the encoded representation of the predetermined temporal fragment, and a fragment length value indicating a temporal length of the predetermined temporal fragment from the beginning of the reconstructed version of the predetermined fragment to the fragment boundary with which the beginning of the reconstructed version of the succeeding temporal fragment coincides, and/or a truncation length value indicating a temporal length of the portion of the trailing audio frame or the difference between the temporal length of the portion of the trailing audio frame and the temporal length of the trailing audio frame, when said computer program is run by a computer. 
         [0020]    A basic idea underlying the present application is that audio video synchronization and alignment or alignment of audio to some other external clock may be rendered more effective or easier when fragment grid and frame grid are treated as independent values, but when, nevertheless, for each fragment the frame grid is aligned to the respective fragment&#39;s beginning. A compression effectiveness lost may be kept low when appropriately selecting the fragment size. On the other hand, the alignment of the frame grid with respect to the fragments&#39; beginnings allows for an easy and fragment-synchronized way of handling the fragments in connection with, for example, parallel audio video streaming, bitrate adaptive streaming or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which: 
           [0022]      FIG. 1  shows a schematic diagram of a temporal fragment containing video and audio where the video and audio fragments are time-aligned in accordance with an embodiment of the present application; 
           [0023]      FIG. 2  shows a semi-schematic and block diagram of an encoder, the audio content encoded thereby and the encoded data stream generated thereby in accordance with an embodiment; 
           [0024]      FIG. 3  shows a semi-schematic and block diagram of a decoder fitting to the encoder of  FIG. 2  in accordance with an embodiment; 
           [0025]      FIG. 4  shows a schematic diagram of windows, time-domain portions involved in the encoding/decoding process in accordance with an embodiment according to which transform-based coding/decoding is used for coding/decoding the frames, namely by applying a lapped transform; 
           [0026]      FIG. 5  shows a schematic diagram illustrating the generation of immediate playout information in accordance with an embodiment; 
           [0027]      FIG. 6  shows a schematic diagram illustrating the case of a configuration change in the audio content in accordance with an embodiment showing that, for example, immediate playout information may be missing in case of a configuration change at the beginning of a respective temporal fragment, or where the immediate playout information of such temporal fragment encodes zero samples instead; 
           [0028]      FIG. 7  shows a packetized DASH segment delivered over ROUTE in accordance with [1] for comparison purposes; and 
           [0029]      FIG. 8  shows two consecutive fragments carrying audio and video in accordance with current fragmentation concept according to which the audio fragmentation involves different fragmented durations. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Before describing various embodiments of the present application, the advantages provided by, and the thoughts underlying, these embodiments are described first. In particular, imagine that an audio content is to be coded so as to accompany a video frame composed of a sequence of video frames. The problem is as outlined above in the introductory portion of the present application: nowadays audio codecs operate on a sample and frame basis which is no integer fraction or integer multiple of the video framerate. Accordingly, the embodiments described hereinafter use encoding/decoding stages operating in units of “usual” frames for which they are optimized. On the other hand, the audio content is subject to the audio codec underlying these encoding/decoding stages in units of temporal fragments which may be one or more, advantageously one to five, or even more advantageously one or two video frames long. For each such temporal fragment, the frame grid is chosen to be aligned to the beginning of the respective temporal fragment. In other words, the idea underlying the subsequently described embodiments is to produce audio fragments which are exactly as long as the corresponding video frame, with this approach having two benefits: 
         [0031]    1) The audio encoder may still work on an optimized/native frame duration and does not have to leave its frame grid on fragment boundaries. 
         [0032]    2) Any audio delay may be compensated by the usage of immediate playout information for the encoded representations of the temporal fragments. Splicing can happen at each fragment boundary. This reduces the overall complexity of the broadcast equipment significantly. 
         [0033]      FIG. 1  shows an example for an audio fragment generated in a manner in accordance with an example set out below, which audio fragment accompanies a corresponding video fragment. Both audio fragment and video fragment are illustrated in a manner corresponding to FIG. B. That is, at  2 , i.e. the top row of  FIG. 1 ,  FIG. 1  illustrates the video fragment as being composed of a number N of frames 4, i.e. video frames, wherein the frames are shown as squares sequentially arranged row-wise from left to right along their temporal playout order as illustrated by temporal axis t. The left hand edge of frame  0  and the right hand edge of frame  59  are shown as being registered to the beginning and end of the fragment, meaning the temporal length T fragment  of the fragment is an integer multiple of the video frame length, the integer multiple N here being exemplarily  60 . Temporally aligned to the video fragment  2 ,  FIG. 2  illustrates there below an audio fragment  10  having encoded thereinto the audio content accompanying the video fragment  2  in units of frames or access units  12 , here illustrated as rectangles extending horizontally, i.e. temporally, at a temporal pitch which shall illustrate their temporal frame length and this audio frame length is, unfortunately, such that the temporal length T fragment  of the audio fragment  10  is no integer multiple of this frame length T frame . For example, the relationship between the frame length T frame  and the corresponding frame length of the video frames T videoframe  may be such that the ratio therebetween is either irrational or the ratio therebetween may be represented by a proper fraction, completely reduced, where the numerator times the denominator is higher than, for example, 1000, so that a fragment length which would be a multiple of both the video frame length T video frame  and the audio frame length T frame  would be disadvantageously high. 
         [0034]      FIG. 1  illustrates that, accordingly, a last or trailing frame, namely access unit  46 , temporally covers a temporal portion of the audio content which exceeds the trailing end  14  of the audio fragment  10 . Later on, it will be shown that the portion  16  exceeding or succeeding the trailing end  14  may be truncated or disregarded at the decoder side in playout, or that the whole trailing frame is actually not encoded with the decoder merely flushing its internal states so as to fill the “temporal hole” of the portion of the trailing frame as far as overlapping with the temporal fragment  10 . 
         [0035]    For illustration purposes,  FIG. 1  illustrates at the lower half thereof, namely at  16 , that the bit budget available for the temporal fragment composed of video and audio, namely T fragment ·R with R being a bitrate, could be used for carrying the video data  18  into which the video frames  4  of fragment  2  are coded, the audio data  20  into which the audio content of audio fragment  10  are coded, header data  22  and  24  of both, respectively, configuration data  26  indicating, for example, the spatial resolution, temporal resolution and so forth at which the video frames  4  are coded into data  18  and the configuration such as the number of channels at which the audio frames  12  of fragment  2  are coded into data  20  as well as a manifest or media presentation description here illustratively included into the data for the co-aligned fragments  2  and  10  so as to indicate, for example, the versions at which video and audio are available, the versions differing in bitrate. It should be understood that the example of  FIG. 1  is merely illustrative and that the embodiments described hereinafter are not restricted to being used in connection with bitrate adaptive streaming and sending a manifest to the client and so forth.  FIG. 1  shall merely illustrate the common concept of the below-explained embodiments according to which the audio fragmentation is rendered fully aligned to the video fragmentation by aligning the audio frames  12  to beginning  30  of fragments  10  which, in turn, are chosen to be, for example, completely aligned to the video frames  4 . 
         [0036]      FIG. 1  thus shows an audio and a video fragment, both being aligned in the described way. In the example of  FIG. 1 , the video and audio fragment were chosen to have a constant temporal length T fragment  of 
         [0000]    
       
         
           
             
               
                 1001 
                 1000 
               
                
               
                   
               
                
               sec 
             
             = 
             
               1.001 
                
               
                   
               
                
               sec 
             
           
         
       
     
         [0000]    which is equivalent to 60 video frames at the NTSC frame rate of 59.94 Hz. 
         [0037]    The last audio frame of each audio fragment, here AU  46 , is for example truncated to match the fragment duration. In the given example, the last audio frame reaches from sample  47104  to  48127  wherein a zero-based numbering has been chosen, i.e. the first audio sample in the fragment is numbered zero. This leads to a fragment size of a number of samples which is slightly longer than needed, namely  48128  instead of  48048 . Therefore, the last frame is cut right after the 944 th  sample. This can be accomplished by using, for example, an edit list contained for example in the header data  24  or in the configuration data  26 . The truncated part  16  can be encoded with less quality, for example. Alternatively, there would be the possibility to not transmit all audio frames  12 , but to leave out, for example, the coding of the last frame, here exemplarily AU  46 , since the decoder can normally be flushed depending on the audio configuration. 
         [0038]    In the embodiments described further below, it will be shown that measures may be taken to counteract the problem that the decoder which operates, for example, on an overlapping windows function will lose its history and is not able to produce a full signal for the first frame of the following fragment. For that reason, the first frame, in  FIG. 1  exemplarily AU 0 , is coded as an IPF frame allowing immediate playout (IPF=Immediate Playout Frame). It is placed right at the beginning of the respective fragment and any audio fragment, respectively. Likewise, the first video frame  4  may be an IDR frame (IDR=Instantaneous Decoding Refresh). 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Bitrate overhead 
               
             
          
           
               
                 Overhead (worst-case)            
                 No sbr (1 sec)            
                 Sbr 2:1 (1 sec)            
                 No sbr (2 sec)            
                 Sbr 2:1 (2 sec)            
                 No sbr (0.5 sec)            
                 Sbr 2:1 (0.5 sec)            
               
               
                   
               
             
          
           
               
                 Fragment size (sec): 
                 1.001 
                 1.001 
                 2.002 
                 2.002 
                 0.5005 
                 0.5005 
               
               
                 Frame size (samples): 
                 1024 
                 2048 
                 1024 
                 2048 
                 1024 
                 2048 
               
               
                 Samplingrate: 
                 48000 
                 48000 
                 48000 
                 48000 
                 48000 
                 48000 
               
               
                 Preroll (aus): 
                 5 
                 3 
                 5 
                 3 
                 5 
                 3 
               
               
                 Normal aus/fragment: 
                 46.921875 
                 23.4609375 
                 93.84375 
                 46.921875 
                 23.4609375 
                 11.73046875 
               
               
                 Aligned aus/fragment: 
                 52 
                 27 
                 99 
                 50 
                 29 
                 15 
               
               
                 Overhead: 
                 10.80% 
                 15.10% 
                 5.50% 
                 6.60% 
                 23.60% 
                 27.90% 
               
               
                   
               
             
          
         
       
     
         [0039]    The above table gives an example for the expected bitrate overhead if no optimization would be applied. It can be seen that the overhead depends strongly on the used fragment duration T fragment . Depending on the broadcaster&#39;s requirement, it is feasible to align only every second or third fragment, respectively, i.e. choosing the audio fragments to be longer. 
         [0040]      FIG. 2  shows an encoder for encoding audio content in units of the temporal fragments  10  of a fragment grid  32  into an encoded data stream  34 . The encoder is generally indicated using reference sign  20  and comprises an encoding stage  36  and a fragment provider  38 . The encoding stage  36  is configured to encode audio content in units of frames  12  of a frame grid and the fragment provider  38  is configured to provide the audio content  31  to the encoding stage  36  in units of temporal fragments  10  so that each temporal fragment is encoded by the encoding stage  36  into an encoded representation  38  of the respective temporal fragment  10 , wherein the fragment provider  38  is configured to provide the audio content  31  to the encoding stage  36  in units of the temporal fragments  10  such that each temporal fragment of the respective frame grid of frames  12  is temporally aligned to the beginning  30  of the respective temporal fragment  10  so that the beginning  30  coincides with a frame boundary  42  of the respective frame grid of frames  12 . That is, as further described hereinafter, fragment provider  38  may provide encoding stage  36 , temporal fragment  10  wise, with a portion  44  of the audio content  31  which includes the temporal fragment  10  currently provided and optionally a portion  46  of the audio content  31  temporally preceding the current temporal fragment  10 , and a portion  48  temporally succeeding the current temporal fragment  10 . In providing the encoding stage  36  with a current portion  44 , the current temporal fragment  10  is temporally aligned  50  by the fragment provider  38  such that the frame boundaries  42  comprise one frame boundary which coincides with the beginning  30  of the current temporal fragment  10 . As described above with respect to  FIG. 1 , owing to the fact that the temporal length of the temporal fragment  10  being a non-integer multiple of the temporal length of the frames  12 , a trailing frame  12   a  merely partially covers or temporally overlaps with a temporal fragment  10  with a portion  16  thereof covering with the succeeding portion  48  of the audio content. 
         [0041]    Before describing in detail the functionality of the encoder of  FIG. 2 , reference is made to  FIG. 3 , which shows a corresponding decoder in accordance with an embodiment. The decoder of  FIG. 3  is generally indicated using reference sign  60  and is configured to decode audio content  31  in units of temporal fragments  10  from the encoded data stream  34 . The decoder  60  comprises an input interface  62  which receives encoded representations of the temporal fragments. As illustrated in  FIG. 3  using hatching and as already explained with respect to  FIG. 2 , for each temporal fragment  10 , an encoded representation  40  thereof is present in the data stream  34 . Each encoded representation  40  has encoded thereinto its associated temporal fragment  10  in units of the aforementioned frames  12  temporally aligned to the beginning  30  of the respective temporal fragment  10  so that the beginning  30  coincides with a frame boundary  42  of the frame grid. 
         [0042]    The decoder  60  further comprises a decoding stage  64  configured to decode reconstructed versions  66  of the temporal fragments  10  from the encoded representations  40 . That is, decoding stage  64  outputs, for each temporal fragment  40 , a reconstructed version  66  of the audio content as covered by the temporal fragment  10  to which the respective encoded representation  40  belongs. 
         [0043]    The decoder  60  further comprises a joiner  68  configured to join, for playout, the reconstructed versions  66  of the temporal fragments  10  together with, inherently, aligning the beginnings of the reconstructed versions  66  of the temporal fragments so as to coincide with the fragment boundaries of the fragment grid, i.e. at the beginnings  30  of the fragment grid, as the individual frame grids of the fragments  10  are registered thereto. 
         [0044]    Thus, encoder  20  and decoder  60  of  FIGS. 2 and 3  operate as follows. The encoder  20  encodes each temporal fragment  10  into a corresponding encoded representation  40  such that the frame grid of frames  12  is aligned to the beginning  30  of the corresponding temporal fragment  10  such that a first or leading frame  12   b  immediately starts at beginning  30 , i.e. the beginnings of temporal fragment  10  and first frame  12   b  coincide. The problem how the encoding stage  36  treats the trailing frame  12   a , which merely partially overlaps the temporal fragment  10  may be solved differently, as set out below. Further, as the encoding stage  36  realigns its frame grid for each temporal fragment  10 , encoding stage  36  encodes the temporal fragments  10  into their corresponding encoded representation  40  in a completely self-contained manner, i.e. independent from the other temporal fragments. Nevertheless, the encoding stage  36  encodes the temporal fragments  10  into their corresponding encoded representations  40  such that immediate playout is allowed at the decoding side for each temporal fragment. Possible implementation details are set out below. In turn, the decoder  60  reconstructs from each encoded representation  40  a reconstructed version  66  of the corresponding temporal fragment  10 . The reconstructed version  66  may be as long as the corresponding temporal fragment  10 . To this end, as described further below, decoding stage  64  may perform flushing in order to extend the temporal length of the reconstructed version  66  to the temporal length of the temporal fragments  10 , or decoding stage  64  and joiner  66  may, as discussed below, cooperate in order to truncate or disregard temporal portions of the reconstructed version  66 , which would otherwise exceed the temporal length of the temporal fragments. The decoding stage  64 , in performing the decoding of the encoded representations  40 , also uses the frame grid, i.e. performs the decoding in units of the frames  12  and substantially performs an inverse of the encoding process. 
         [0045]    In the following, the possibility is discussed according to which the encoding stage  36  also attends to encoding the trailing frame  12   a  into the corresponding encoded representation  40 , and that the decoder attends to a truncation of the corresponding overhanging portions of the reconstructed version  66 . In particular, in accordance with this example, the encoding stage  36  and the fragment provider  38  may cooperate such that, for a current temporal fragment  10 , the encoding of this temporal fragment  10  into the encoded representation  40  is continued beyond the trailing end  70  of the current temporal fragment  10  as far as the trailing frame  12   a  is concerned. That is, the encoding stage  36  also encodes the overhanging portion  16  of the audio content into the encoded representation  40 . In doing so, however, the encoding stage  36  may shift the bitrate spent for encoding this trailing frame  12   a  into the encoded representation  40  from the overhanging portion  16  to the remaining portion of trailing frame  12   a , i.e. the portion temporally overlapping with the current temporal fragment  10 . For example, the encoding stage  36  may lower the quality at which the overhanging portion  16  is coded into the encoded representation  40  compared to the quality at which the other portion of trailing frame  12   a  is coded into the encoded representation  40 , namely the one belonging to the current temporal fragment  10 . In that case, the decoding stage  64  would accordingly decode from this encoded representation  40  a reconstructed version  66  of the corresponding temporal fragment  10  which temporally exceeds the temporal length of the temporal fragment  10 , namely as far as the overhanging portion  16  of the trailing frame  12   a  is concerned. The joiner  68 , in aligning the reconstructed version  66  with the fragmentation grid, i.e. with the fragments&#39; beginnings  30 , would truncate the reconstructed version  66  at the overhanging portion  16 . That is, joiner  68  would disregard this portion  16  of the reconstructed version  66  in playout. The fact that this portion  16  might have been coded at lower quality as explained above, is accordingly transparent for the listener of the reconstructed audio content  31 ′, which is the result of the joining of the reconstructed versions  66  at the output joiner  68 , as this portion is replaced, in playout, by the beginning of the reconstructed version of the next temporal fragment  10 . 
         [0046]    Alternatively, the encoder  20  may be operative to leave out the trailing frame  12   a  in encoding a current temporal fragment  10 . Instead, the decoder may attend to fill the non-encoded portion of the temporal fragment  10 , namely the one with which the trailing frame  12   a  partially overlaps, by flushing its internal state as described exemplarily further below. That is, the encoding stage  36  and fragment provider  38  may cooperate such that, for a current temporal fragment  10 , the encoding of this temporal fragment into its encoded representation  40  is seized at the frame  12  immediately preceding the trailing frame  12   a . The encoding stage may signal within the encoded representation  40  a flush signalization instructing the decoder to fill the remaining, thus non-encoded portion of the temporal fragment  10 , namely the one which overlaps with the trailing frame  12   a , by means of flushing internal states of the encoder as manifesting themselves up to the frame  12  immediately preceding the trailing frame  12   a . At the decoder side, the coding stage  64  may be responsive to this flush signalization so as to, when decoding the corresponding encoded representation  40 , generate the reconstructed version  66  of the temporal fragment  10  corresponding to this encoded representation  40  within the portion at which the temporal fragment  10  and a trailing frame  12   a  overlap by flushing its internal states of the decoding stage  64  as manifesting themselves up to the immediately preceding frame  12  of the trailing frame  12   a . 
         [0047]    In order to illustrate the flushing procedure in more detail, reference is made to  FIG. 4 , which illustrates the case of generating a non-encoded remainder portion of the reconstructed version  66  for the exemplary case of the encoding and decoding stages operating on the basis of a transform codec. For example, a lapped transform may be used to encode the frames. 
         [0048]    That is, the encoding stage  36  uses one window  72  of several windows in order to weight corresponding interval(s)  74  of the audio content with spectrally decomposing the resulting windowed portion by use of a frequency decomposing transform such as an MDCT or the like. The windowed portion  74  covers and temporally extends beyond the current frame&#39;s  12 ′ boundaries.  FIG. 4 , for instance, illustrates that the window  72  or windowed portion  74  temporally overlaps with two frames  12  preceding the current frame  12 ′ at two frames succeeding the current frame  12 ′. Thus, the encoded representation  40  for a current temporal fragment  10  comprises the coding of the transform of the windowed portion  74  as this coding  76  is the coded representation of frame  12 ′. The decoding stage  64  performs the inverse in order to reconstruct the frames  12  of the temporal fragments  10 : it decodes the transform  76  by means of, for example, entropy decoding, performs the inverse transform so as to result in a windowed portion  74  which covers the current frame  12 ′ to which transform  76  belongs, but the decoding stage  64  additionally performs an overlap-add process between consecutive windowed portions  74  so as to obtain the final reconstruction of the audio content  31 ′. The overlap-add process may be performed by joiner  68 . This means the following:  FIG. 4 , for example, assumes that a current frame  12 ′ is the penultimate frame immediately preceding the trailing frame  12   a  of a current temporal fragment  10 . The decoding stage  64  reconstructs the audio content covered by this penultimate frame  12 ′ by performing, as just outlined, the inverse transformation onto the transform  76  so as to obtain a time-domain portion  76  within the windowed portion  74 . As explained above, this time-domain portion  76  temporally overlaps with the current frame  12 ′. Other time-domain portions having been obtained by inverse transforming coded transforms of temporally neighboring frames of current frame  12 ′ temporally overlap, however, with the current frame  12 ′ as well. 
         [0049]    In  FIG. 4  this is illustrated for windowed portions belonging to the two preceding frames of current frame  12 ′ and indicated reference sign  78  and  80 . A complete reconstruction of frame  12 ′ is however obtained by the overlap-add process which adds-up the portions of all time-domain portions  76 ,  78  and  80  resulting from inverse transforms applied onto coded transform  76  of frame  12 ′ and neighboring frames thereof, as overlapping the current frame  12 ′ temporally. For the last or trailing frame  12   a , this means the following. Even if the encoding stage  36  does not code the transform(s) of the windowed portion for this trailing frame  12   a  into the encoded representation  40 , the decoder is able to obtain an estimation of the audio content within this trailing frame  12   a  by adding-up all time domain portions temporally overlapping the trailing frame  12   a  as obtained by reverse transforming the coded transforms  76  of one or more previous frames, i.e. of frame  12 ′ and optionally one or more frames  12  preceding the penultimate frame  12 ′ depending on window size, which may be varied compared to  FIG. 4 . For example, the window size may be such that the temporal overlap with temporally preceding frames is greater than the temporal overlap with succeeding frames. Moreover, the temporal overlap may merely involve the immediately preceding and/or immediately succeeding frame of a currently coded frame. 
         [0050]    Different possibilities exist with respect to the manner in which the decoder  60  is informed of the size of overhanging portion  16 . For example, the decoder  60  may be configured to convey truncation information related to this size within the data stream  34  by way of the truncation information comprising a frame length value and a fragment length value. The frame length value could indicate T frame  and the fragment length value T fragment . Another possibility would be that the truncation length value indicates the temporal length of the overhanging portion  16  itself or the temporal length of the portion at which the temporal fragment  10  and the trailing frame  12   a  temporally overlap. In order to allow immediate playout of the reconstructed version  66  of each temporal fragment  10 , the encoding stage  36  and fragment provider  38  may cooperate so that, for each temporal fragment  10 , the encoded representation  40  is also provided with immediate playout information which relates to the portion  46  temporally preceding the respective temporal fragment  10 . For example, imagine that the lapped transform referred to in  FIG. 4  is a lapped transform introducing aliasing, such as an MDCT. In that case, without a transform coded version of the preceding portion  46 , a decoder would not be able to reconstruct a current temporal fragment  10  at its beginning, such as within the first one or more frames  12  thereof without aliasing. Accordingly, in order to perform the time domain aliasing cancellation by means of the overlap-add process, the immediate playout information conveyed within the encoded representation  40  could pertain to a transform coded version of the preceding portion  46  with the encoding and decoding stages using the lapped transform coding process as already illustrated with regard to  FIG. 4 . 
         [0051]    Although it has not been discussed in more detail above, it is noted that encoding stage  36  and/or decoding stage  64  could be composed of two or even more cores. For example,  FIG. 2  illustrates that the encoding stage could comprise a first encoding core  90  and a second encoding core  92  and likewise, additionally or alternatively,  FIG. 3  shows that decoding stage  64  could comprise a first decoding core  94  and a second decoding core  96 . Instead of sequentially encoding/decoding the respective temporal fragments  10  and corresponding encoded representations  40 , the encoding/decoding procedure performed with respect to each of these pairs of temporal fragments  10  and encoded representations  40  could be performed in a pipelined manner with alternately engaging cores  94  and  96  (and  90  and  92 ) with a decoding/encoding of the sequence of temporal fragments  10  and the encoded representations  40 , respectively. 
         [0052]    Thus, in accordance with the embodiment of  FIG. 2 , the audio encoder aligns the first audio frame  12   b  with the beginning  30  of the respective temporal fragment  10 . In order to enable a gapless or immediate playout of the respective constructed version  66  of that temporal fragment  10  with no audible artifacts at the decoding side, the encoder described above operates or words on two different frame grids at fragment boundaries. It was also mentioned that in order to allow for an immediate playout of the individual reconstructed versions  66  at the fragment&#39;s beginning  30 , depending on the audio codec underlying the encoding/decoding stages, immediate playout information may be conveyed within the encoded representations. 
         [0053]    For example, the first frame  12   b  of each temporal fragment may be coded as an immediate playout frame IPF. Such IPF being placed at a beginning of each new temporal fragment may, for instance, cover the whole decoder delay. In order to illustrate this again, reference is made to  FIG. 5 , which shows a portion out of an audio content around a fragment boundary between two temporal fragments  10   a  and  10   b . The frames  12  in units of which the temporal fragments  10 , and  10   b  are coded/decoded are shown in  FIG. 5  as well. In particular,  FIG. 5  reveals that the trailing frame  12   a  of temporal fragment  10 , temporally overlaps the first frame  12   b  of the frames of the frame grid using which the temporal fragment  10   b  is coded/decoded. In particular, it is the portion  16  which extends beyond the trailing end of temporal fragment  10 , and the beginning  30  of temporal fragment  10   b  of the trailing frame  12   a , which temporally overlaps with the first frame  12   b  of temporal fragment  10   b . In encoding the first frame  12   b , the encoding state additionally encodes into the encoded representation  40  for temporal fragment  10   b  immediate playout information  98 , namely here exemplarily coding  100  of five pre-roll frames  12  of the frame grid for coding/decoding the temporal fragment  10   b  preceding the first frame  12   b , the pre-roll frames being indicated by “AU- 5 ” to “AU- 1 ” in  FIG. 1 . These pre-roll frames thus span the aforementioned preceding portion  46 . The encodings  100  may, as outlined above with respect to  FIG. 4 , relate to transform coding version of the audio content within the pre-roll frames so as to allow the decoder side to perform time domain aliasing cancelation using the time-domain portions surrounding these-roll frames using inverse transformation and using their parts extending into temporal fragment  10   b  so as to perform the time-domain aliasing cancelation in the overlap-add process. 
         [0054]    The encoder is aware of the exact fragment duration. As explained above, in accordance with an embodiment, the overlapping audio part  16  may be encoded two times with different frame grids. 
         [0055]    A brief statement is performed with respect to the “self-contained manner” at which the individual temporal fragments  10  are coded into their encoded representations  40 . Although this self-contained manner could also pertain to configuration data such as coding parameters pertaining to more seldom changing data such as number of encoded audio channels or the like, so that each encoded representation  40  could comprise this configuration data, it would alternatively be possible that such seldom changing data, i.e. configuration data, is conveyed to the decoding side out of band, not within each encoded representation  40  instead of being included in each encoded representation  40 . If included in the encoded representation, the configuration data may be transmitted in another transport layer. For example, the configuration may be transmitted in the initialization segment, and the IPF frame  12   b  of each temporal fragment could be freed from carrying the configuration data information. 
         [0056]    As far as the decoding side is concerned, the above description of  FIG. 3  revealed that the decoder be configured to decode pre-roll frames, i.e. frames preceding the first frame  12   b  for each temporal fragment. The decoder may attend to this decoding irrespective of whether the configuration changes from the preceding temporal fragment to a current temporal fragment. This of course impacts the decoder&#39;s overall performance, but advantageously, a decoder may already have to fulfill a requirement according to which the decoder is able to decode an IPF on each fragment boundary such as, for example, in accordance with a worst-case adaptive streaming use-case, so that no additional requirement is imposed in the case of such cases. As far as the above mentioned truncation information is concerned, it should be noted that the signaling thereof may be done on the bitstream level, or at some other transport layer such as with system level tools. 
         [0057]    Finally,  FIG. 6  shows a case where the audio content  31  to be encoded shows a configuration change such as a change in a number of audio channels, at some point in time  110 , namely at a fragment boundary between two temporal fragments  10 . For example, immediately preceding time instant  110 , a first configuration such as stereo applies, whereas after time instant  110 , the audio content  31  is for example a five-channel audio scene. The audio data stream  34  comprises the configuration data information. Thus, it is clear from the data stream  34  that the data stream&#39;s encoded representations of the temporal fragments  10  preceding time instant  110  are coded according to the first configuration, and that the second configuration is used for encoding the temporal fragments  10  succeeding the time instant  110 . 
         [0058]      FIG. 6  also shows the immediate playout information  98  of the encoded representations  40 . In the case of the temporal fragment  10  preceding time instant  110 , the immediate playout information  98  may be derived as described above with respect to  FIG. 5 , for example. However, the situation is different for the temporal fragment  10  immediately starting at time instant  110 . Here, the audio content  39  does not allow for forming the immediate playout information  98  for the encoded representation  40  of the temporal fragment immediately starting at time instant  110 , as the audio content  39  in the second configuration is not elevatable at the time prior to the time instant  110 . A zero-signal may be coded as immediate playout information  98  with respect to this temporal fragment  10  starting at time instant  110 , instead. 
         [0059]    That is, in case of a configuration change, the encoder may encode zero samples since there is no actual audio signal available for the past, such as, for example, when switching from mono to 5.1 or the like. A possible optimization would be to generate this zero frame, i.e. zero pre-roll frame, on the decoder side and to transmit only the encoding of the first frame  12   b  of the first temporal fragment. That is, in such a case the immediate playout information  98  could be left away completely. 
         [0060]    Thus, the above embodiments allow the delivery of audio and video content over a transmission channel with either fixed or variable bitrate and allow, in particular, audio video synchronization and enable advanced use-cases such as splicing. As mentioned above, the encoded data stream as encoded above, may also render easier a synchronization with other clocks such as clocks prescribed by other media signals. The encoders described above allow for an adaptation of an existing audio frame length. The length of the temporal fragments may be set depending on the application&#39;s needs. The encoder embodiments form the encoded data stream in tranches of encoded representation of the temporal fragments which may, for instance, but not exclusively, be made the subject of adaptive streaming by using these fragments as the fragments of a media representation. That is, the coded data stream, composed of the resulting fragments, may be offered to a client by server via an adaptive streaming protocol, and the client may retrieve the data stream fragments with, maybe, an add inserted thereinto, via the protocol and forward same to the decoder for decoding. But this is not mandatory. Rather, splicing may be advantageously be affected by the formation of the inventive encoded data stream even in other application scenarios. The above described embodiments may be implemented or used in connection with MPEG-H audio codec with the audio frames being MPEG-H audio frames, but the above embodiments are not restricted to the usage of this codec but may be adapted to all (modern) audio codecs. 
         [0061]    Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be executed by (or using) a hardware apparatus, like for example, a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some one or more of the most important method steps may be executed by such an apparatus. 
         [0062]    The inventive spliced or splicable audio data streams can be stored on a digital storage medium or can be transmitted on a transmission medium such as a wireless transmission medium or a wired transmission medium such as the Internet. 
         [0063]    Depending on certain implementation requirements, embodiments of the invention can be implemented in hardware or in software. The implementation can be performed using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable. 
         [0064]    Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed. 
         [0065]    Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer. The program code may for example be stored on a machine readable carrier. 
         [0066]    Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier. 
         [0067]    In other words, an embodiment of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer. 
         [0068]    A further embodiment of the inventive methods is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier, the digital storage medium or the recorded medium are typically tangible and/or non-transitionary. 
         [0069]    A further embodiment of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein. The data stream or the sequence of signals may for example be configured to be transferred via a data communication connection, for example via the Internet. 
         [0070]    A further embodiment comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein. 
         [0071]    A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein. 
         [0072]    A further embodiment according to the invention comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver. The receiver may, for example, be a computer, a mobile device, a memory device or the like. The apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver. 
         [0073]    In some embodiments, a programmable logic device (for example a field programmable gate array) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein. Generally, the methods are advantageously performed by any hardware apparatus. 
         [0074]    The apparatus described herein may be implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer. 
         [0075]    The methods described herein may be performed using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer. 
         [0076]    While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention. 
       DEFINITIONS AND ABBREVIATIONS 
       [0077]    AAC Advanced Audio Coding 
         [0078]    ATSC Advanced Television Systems Committee 
         [0079]    AU Audio Access Unit 
         [0080]    DASH Dynamic Adaptive Streaming over HTTP 
         [0081]    DVB Digital Video Broadcasting 
         [0082]    IPF Instantaneous Playout Frame 
         [0083]    MPD Media Presentation Description 
         [0084]    MPEG Moving Picture Experts Group 
         [0085]    MMT MPEG media transport 
         [0086]    NTSC National Television Systems Committee 
         [0087]    PAL Phase-Alternating-Line-Verfahren 
       REFERENCES 
       [0088]    [1] “Delivery/Sync/FEC-Evaluation Criteria Report”, ROUTE/DASH 
         [0089]    [2] ISO/IEC 23008-3, “Information technology—High efficiency coding and media delivery in heterogeneous environments—Part 3: 3D audio” 
         [0090]    [3] ISO/IEC 23009-1, “Information technology—Dynamic adaptive streaming over HTTP (DASH)—Part 1: Media presentation description and segment formats” 
         [0091]    [4] ISO/IEC 23008-1, “Information technology—High efficiency coding and media delivery in heterogeneous environments—Part 1: MPEG media transport (MMT)”