Abstract:
An apparatus comprising an encoder circuit, a recordable medium, and a decoder circuit. The encoder circuit may be configured to generate (i) a first recordable signal and (ii) a second recordable signal in response to an input bitstream having program information and commercial information. The recordable medium may be configured to record the first and second recordable signals and present an intermediate signal containing program information and transition information. The decoder circuit may be configured to generate an output signal in response to the intermediate signal. The decoder circuit uses the transition information within the intermediate signal to detect or skip the commercial information.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to video processing generally and, more particularly, to a method and/or apparatus for implementing a compressed domain commercial detect/skip feature.  
       BACKGROUND OF THE INVENTION  
       [0002]     Conventional commercial skip features are frequently available for VCRs, DVD recorders, personal video recorders (PVRs) and other devices for recording and/or timeshifting video. Conventional solutions work in the sampled (or uncompressed) domain. In particular, conventional approaches work on decoded/raw video and/or audio.  
         [0003]     For a digital video recorder (DVR) or personal video recorder (PVR), conventional approaches are inefficient when a raw bitstream is being directly stored to a recordable medium (e.g., a harddrive or a DVD). With such direct recording, a commercial detect system needs to either (a) decode a portion of the entire bitstream (i.e., lookahead) for commercial detection or (b) provide offline/background video decoding with commercial detection. Both conventional approaches are wasteful of resources. In particular, both conventional approaches need the video to be fully decoded in order to perform the commercial detection.  
         [0004]     It would be desirable to perform a commercial detect and/or skip either entirely or partially in the compressed domain.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention concerns an apparatus comprising an encoder circuit, a recordable medium, and a decoder circuit. The encoder circuit may be configured to generate (i) a first recordable signal and (ii) a second recordable signal in response to an input bitstream having program information and commercial information. The recordable medium may be configured to record the first and second recordable signals and present an intermediate signal containing program information and transition information. The decoder circuit may be configured to generate an output signal in response to the intermediate signal. The decoder circuit uses the transition information within the intermediate signal to detect or skip the commercial information.  
         [0006]     The objects, features and advantages of the present invention include providing a commercial detect and/or skip that may (i) operate in the compressed domain, (ii) encode syntax indications in a compressed bitstream, (iii) in some cases, partially decode the bitstream, (iv) avoid unnecessary decoding and/or (v) save resources by reducing and/or eliminating unnecessary decoding. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     These and other objects, features and advantages of the present invention will be apparent from the following detailed description and the appended claims and drawings in which:  
         [0008]      FIG. 1  is a block diagram of the present invention;  
         [0009]      FIG. 2  is a block diagram of an alternate embodiment of the present invention; and  
         [0010]      FIG. 3  is a block diagram of another alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]     Referring to  FIG. 1 , a block diagram of a system  100  is shown in accordance with a preferred embodiment of the present invention. The system  100  may be used to perform commercial detection during encoding by using syntax indications. The system  100  generally comprises a block (or circuit)  102 , a block (or circuit)  104 , a block (or circuit)  106  and a block (or circuit)  108 . The circuit  102  may be implemented as a content provider. The circuit  104  may be implemented as an encoder circuit. The circuit  106  may be implemented a recordable medium. The circuit  108  may be implemented as a decoder circuit.  
         [0012]     The content provider  102  may provide a signal (e.g., INPUT). The signal INPUT may be an uncompressed audio/video signal. The content provider  102  may be implemented as a cable television service, a satellite provider, an internet provided audio/video stream, or other appropriate content provider. The encoder circuit  104  may have an input  110  that may receive the signal INPUT, an output  112  and an output  114 . The output  112  may present a signal (e.g., TRANSITION) to an input  116  of the recordable medium  106 . The signal TRANSITION may be used to store information related to commercials. The output  114  may present a signal (e.g., COMPRESSED) to an input  118  of the recordable medium. The signal COMPRESSED may be a compressed audio/video bitstream. The signal COMPRESSED and the signal TRANSITION may be separately stored in the recordable medium  106 . The recordable medium  106  may have an output  120  that normally presents the signal COMPRESSED to an input  122  of the decoder  108 . The decoder  108  normally presents a signal (e.g., OUTPUT). The signal OUTPUT may be a decompressed audio/video bitstream.  
         [0013]     In one example, the recordable medium  106  may be implemented as a hard disk drive. In one example, a plurality of hard disk drives may be implemented. In another example, a recordable DVD may be implemented. The particular type of recordable medium may be varied to meet the design criteria of a particular implementation.  
         [0014]     During encoding, side-information is stored as the signal TRANSITION. A personal video recorder (PVR) or a digital video recorder (DVR) may be used with the encoder  104  to detect potential commercial transitions and/or commercials and to store indications along with the compressed audio/video bitstream. Since the signal TRANSITION is stored along with the signal COMPRESSED, a commercial detection and/or skip feature may be implemented in the compressed domain. In particular, the compressed domain normally refers to a signal that is digitally stored and/or transmitted prior to decoding. Various compression standards, such as H.263, H.264, Windows Media, etc. may be used to generate a compressed bitstream.  
         [0015]     Referring to  FIG. 2 , a system  100 ′ is shown implementing an alternate embodiment of the present invention. The circuit  100 ′ generally comprises a content provider circuit  102 ′, an encoder circuit  104 ′, a block (or circuit)  105 , a recordable medium circuit  106 ′ and a decoder circuit  108 ′. The encoder  104 ′ generates the signal COMPRESSED that includes one or more syntax elements that indicate when a commercial starts and ends. The circuit  105  may be implemented as a commercial detection block. The circuit  105  may include a bitstream parser circuit  107 .  
         [0016]     The system  100 ′ may use syntax elements encoded in the signal COMPRESSED to indicate a number of fades  110   a - 110   n  already present in standard bitstream syntax. The fades  110   a - 110   n  may be used to detect commercial transitions. Such commercial transitions may include (i) VC-1 intensity compensation syntax fades to/from a constant graylevel, (ii) H.264/MPEG4-AVC weighted prediction syntax where a bitstream parser extracts the relevant syntax elements from the bitstream, and/or (iii) intensity compensation and/or weighted prediction syntax values. Commercial detection may be implemented using these transitions to avoid completely decoding the compressed bitstream).  
         [0017]     Referring to  FIG. 3 , a system  100 ″ is shown comprising a content provider  102 ″, an encoder  104 ″, a recordable medium  106 ″, a decoder  108 ″ and a partial decoder  109 . The system  100 ″ may be used to partially decode a bitstream. The partial decoder  109  receives the signal COMPRESSED from the encoder  104 ″. The partial decoder  109  presents a signal (e.g., PARTIAL). The signal PARTIAL generally comprises an uncompressed bitstream at the DC level.  
         [0018]     The system  100 ″ may use partial video decoding to implement commercial detection. The partial decoding may include combination of partial video decoding along with partial audio decoding. The partial decoder  109  may implement a block DC level decode. Examples of such partial decoding include (i) decoding only DC levels of selected blocks/macroblocks/fields/frames, (ii) decoding some percentage of reference-frame macroblocks and/or slices, (iii) decoding some percentage of all macroblocks and/or slices, (iv) decoding some percentage of key (I-frame) macroblocks and/or slices, (v) not performing a full decode either by not decoding all macroblocks and/or frames and/or fields, (iv) and/or not decoding all coefficients (e.g., decoding only the DC of each transform block). In one example, reference frames may be stored at a reduced resolution (e.g., storing DCs only) to save memory bandwidth. In another example, reconstructing only DC block images may be implemented.  
         [0019]     The present invention may be used to implement a low-complexity commercial detection on compressed bitstreams. While some embodiments of the present invention use a partial decode, none of the three options need a complete video decode.  
         [0020]     The present invention normally allows a lookahead commercial detect, and/or offline/background flagging and classification of commercials. Significant resources may be saved with the present invention in contrast to conventional systems that run a complete decode either well ahead of the currently displayed video (or offline depending on which detection interface is needed).  
         [0021]     In one example, the present invention may be implemented without a decoder. For example, the present invention may be implemented as a method for implementing commercial detection on an arbitrary bitstream, such as an H.264 bitstream, an H.263 bitstream, etc. Such an implementation may involve decoding only a small portion of the bitstream. Such an implementation may be used to look at a combination of a “Prediction Weight Table” that is normally specified for each video slice, and one or more macroblock reference indices that indicate what weights from the table to use for motion compensation in an H.264 video stream to detect fades/transitions for commercial detection. In another example, such an implementation may look only at the DC values of the video transform blocks to detect fades/transitions for commercial detection. In another example, such an implementation may look only at the DC values of the audio transform blocks to detect cuts between commercials for commercial detection. In addition, VC-1 intensity-compensation syntax values may be used. VC-1 intensity-compensation syntax values are similar to the H.264 mechanism to indicate that the temporal prediction should be “scaled” or “faded”, making a good indication of a shot or commercial transition point). In general, the present invention may be implemented to not completely decode the video but to look only at coefficient and/or motion vector bitrate and/or macroblock mode decisions from the compressed stream to detect commercial transitions to be used for commercial detection.  
         [0022]     The present invention may be modified to be used in a variety of compressed domain commercial detection systems. Commercial detection and skipping (both manual and automated) are becoming more pervasive in the marketplace with the increasing adoption of PVRs. Traditional methods for commercial detection (e.g., looking for fade-to-black in the video coinciding with silent audio to identify commercial transition points) are becoming less successful for automated detection of commercials. Some techniques involve more complex analysis and classification of video content, but trade off additional complexity and cost. Such systems may still not be successful, since as more wide spread countermeasures are being designed by broadcasters to defeat such techniques.  
         [0023]     While traditional approaches may continue to be successful for a significant portion of commercial and commercial block detection for some time to come, alternative methods may be implemented to increase successful detection. The compressed domain analysis of the present invention provides many alternative sources of information that may be used for commercial detection. For example, the identification of a video splice point may be implemented through identification of a change in high-level syntax. For example, different encoding strategies may be used for main program and commercials, since each source tends to be generated at a different studio facility. Commercials may be identified in bitstream syntax through the use of different strategies such as (i) scaling lists, (ii) quantization matrices, (iii) picture order count types or patterns, (iv) number of reference frames, (v) use of repeat fields and repeat frames, (vi) group of pictures structure, (vii) user data rates, (viii) scene transition indicators, (ix) recovery point indicators, (x) access unit delimiters, (xi) usage pattern of pan-scan parameters, (xii) film grain models, etc. Such syntax elements may be analyzed to detect changes between program and commercial content.  
         [0024]     While H.264 terminology has been used, similar high level syntax from MPEG-2 and VC-1 may also be used in a similar fashion. For example, it is unlikely that a program and an inserted commercial could successfully use similar film grain models without lending a very unnatural look to one of these sources. Since the program and commercial each may have been initially encoded with a different authoring process, even transcoding and splicing these bitstreams together will often not remove all the high-level syntax differences that identify the individual sources.  
         [0025]     While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.