Abstract:
The invention is a system for recording and reading both program data and acoustical control data and playing back the data to optimize performance of audio reproduction and recreate the effect of an original acoustic environment. The system has a recording apparatus, a playback apparatus and a recording media. The recording apparatus produces recording media having both acoustic control information and audio data. The playback apparatus gives the user some ability to override otherwise automatic parameter adjustments. Optionally, a metadata display system takes information about the physical arrangement of instruments and other characteristics of the recording session and the recording studio and makes that visually available to the listener. A player type register identifies the characteristics of the playback device to cause an adjustment of the characteristics of the playback system.

Description:
FIELD OF THE INVENTION 
   This invention relates to systems for recording and playing back audio information on optical recording media. In particular, it relates to such systems that compensate for the differences between the characteristics of the recording and playback sites. 
   BACKGROUND OF THE INVENTION 
   The present invention is concerned with apparatus and methods for playing back recorded material from media, particularly, but not strictly limited to high density optical recording media such as DVD discs containing acoustic data, e.g., music. For purposes of this disclosure, the term “music” is to be understood throughout to include the possibility of video. A serious limitation of the present systems is that they record music in a studio or a concert hall and leave it to the listener/viewer (herein termed the “listener”) to adjust the playback apparatus to attempt to reproduce the artist&#39;s intended sound in a different playback site, i.e., his home, or car. However, because the recording and playback sites almost always have different acoustic characteristics, it is not feasible for the listener satisfactorily to manage the adjustment of the playback equipment. 
   SUMMARY OF THE INVENTION 
   The present invention provides a system for recording and reading audio visual control data (herein termed “acoustic control data”), together with the musical program data, and playing back the program data in accordance with the acoustical control data to optimize performance of audio reproduction and recreate the original acoustic environment. Basically, it provides a system for incorporating the acoustic control data into the information stored on the media and, during playback, provides components responsive to the control data during the playing back of the musical program. The acoustic control data includes several parameters and may be used to adjust the operation of the playback system as accurately and as often as desired, down to millisecond intervals. 
   The system of the invention comprises a recording apparatus, a playback apparatus and a high density digital recording media, such as DVD. The recording apparatus comprises in addition to the standard equipment, a precision microphone, a controller, a test signal generator and a data multiplexer to produce recording media having both the acoustic control information and the audio data. 
   The playback system comprises a demultiplexer, a customer input interface giving the user some ability to override the otherwise automatic parameter adjustments, optionally a metadata display system that takes information about the physical arrangement of instruments in the recording studio and makes that information visually available to the listener, and a register that identifies the characteristics of the playback apparatus. The playback apparatus further includes data processing components for processing the acoustic program data, these components being dynamically controlled using the acoustic control data. 
   An open and closed loop control scheme is also provided. In the open loop scheme, the acoustic characteristics of local playback site are provided to the playback apparatus by the listener at the playback apparatus. 
   In the closed loop control scheme, the acoustic parameters of the playback site are automatically determined, by generating acoustical test signals and sensing the responses. In either case, the characteristics of the recording and playback sites are compared and used to control the operation of the playback components. 
   The playback apparatus may also include a noise cancellation circuit which receives special information of the acoustic program data from the recording site. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a block diagram for the recording apparatus; 
       FIG. 2  shows a typical sector on a recording media in accordance with the invention; 
       FIG. 3  shows a block diagram of the playback apparatus; 
       FIG. 4  shows details of the delay circuit; 
       FIG. 5  shows a block diagram for the closed loop control configuration; and 
       FIG. 6  shows a block diagram for a noise cancellation circuit in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The invention shall now be described for a particular preferred embodiment in conjunction with the drawings. This preferred embodiment of the present system concerns the generation and replaying of audio data recorded on a pure audio DVD (digital versatile disk). The DVD is an optical recording disc medium having very high data density and MPEG compression of the audio data. The system consists, in addition to the DVD, of a recording apparatus, which herein shall refer to collectively all the equipment involved in generating a DVD media having data representative of a live performance of music or other similar performing activity, and a playback apparatus in which the data from the DVD is reproduced for the listening pleasure of a customer. 
   Referring to  FIG. 1 , the recording apparatus  10  is disposed at a recording site or venue. It includes a plurality of primary microphones  12  used for picking up sounds generated during the performing activity. The signals generated by these microphones  12  are fed to a multichannel recorder  14 . The signals may be stored in the recorder  14 , for later processing or may be fed immediately to a mixer  16 . The mixer  16  combines these signals into a multi-channel and stereo stream of audio data, which for the sake of simplicity, shall be referred to as the program data. 
   An important feature of the present invention is that prior to the performance being recorded, a data generator  18  determines the acoustic conditions of the recording venue and/or control room for the performance and stores the same in a memory  20 . In order to determine these conditions, the generator  18  activates a test signal generator  22  which in response generates a predetermined test signal to an auxiliary speaker  24 . A precision microphone  17  senses the response at the recording locale to the test signal and sends the same to generator  18  and stores it in memory  20 . The recording locale (or venue) is the actual zone where the performance takes place. In addition, the data generator  18  also receives mixing information from the mixer  16  and stores the same in memory  20  as well. Additionally, the producer of the performance may enter specific data regarding the reproduction of the performance to memory  20  via a keyboard  26 . All of this information shall be referred to collectively as acoustical control data. 
   The acoustical control data stored in memory  20  is interleaved with the audio information on the DVD as described more fully below and is used during the playing of the DVD, either to recreate the conditions under which the recording was made and/or other conditions selected by the producer. More particularly, the memory  20  contains information descriptive of the acoustic characteristic of the room where the recording occurs. Of course these characteristics are dependent on the size of the room, the composition of the wall coverings, the height, etc, all of which affect how the sounds are recorded. These characteristics in turn affect certain acoustical properties such as delay, reverberation, and so on, and are determined by data generator  18  from the response to the test signal from generator  22 . 
   In addition, the manner in which the sounds from the different microphones  12  are mixed, i.e. the various proportions or ratios are important when the performance is replayed, especially in a multichannel system since, for most accurate reproduction, the sounds should be replayed by speakers in proportions corresponding to these mixing ratios as described below. Accordingly , this information is also recorded in memory  20 . 
   Finally, the producer may desire to change some of these characteristics. This is especially desirable if when multichannel signals are folded down to generate two-channel stereo sounds. The producer has the ability to define the fold down characteristics using keyboard  26 . 
   The producer may optionally also provide to the data generator various other parameters. Alternatively, this information may be provided automatically from the mixer  16 , the recording equipment or another microphone. Some of these parameters are:
         instrumental placement;   instrument separation partition placement;   peak or RMS limiting in the mixer  16 ;   equalization, compression and other similar recording information;   studio and/or control room dynamic data such as reverb time, delay time, standing waves, ambient noise;   room frequency response, room dynamic information; etc.       

   The acoustical visual control data, or AVCD, is fed to multiplexer  28  which combines the program data with this AVCD and feeds the same to a formatter  30 . Formatter  30  partitions the combined data and, if necessary, adds additional data including for example parity codes, error correction codes, etc., in conformance with a particular DVD standard used. The resulting data is recorded on a DVD by a recording device  32 . 
   A typical data sector  40  shown in  FIG. 2  and consists of a header portion  42  and a data portion  44 . In a typical DVD scheme, the data portion  44 , which normally is reserved to the actual program data is 2048 bytes and the header portion  42 , which carries other types of signals and contains 156 bytes. In the present invention, a small section  46  is carved out, preferably of the data portion  44 , as shown, and dedicated for the AVCD signals. In  FIG. 2 , section  46  is shown at the beginning of the data portion  44 , however it may be disposed at other locations as well. 
   While in  FIG. 2 , AVCD is shown as being provided in a sector  40 , it should be understood that this data need not be repeated in every sector. Instead, the AVCD may be provided in every sector on the DVD or, in an ultimate case, once for each DVD. 
   The other portion of the subject system is the playback apparatus. As shown in  FIG. 3 , this playback apparatus  50  includes a demultiplexer  52 , an AVCD buffer  54  for the AVCD signal and a buffer  56  for the program data. The demultiplexer  52  separates the AVCD and the program data for the respective buffers  54 ,  56  from the incoming data as it is read off the DVD. It also reads the header information and performs other control functions, such as error correction, which do not form a part of this invention. A DVD player which shows details of such a demultiplexer is disclosed in U.S. Pat. No. 5,463,565, incorporated herein by reference. 
   Preferably player  50  is a multichannel audio DVD player capable of generating six channels. (Such players are commonly referred to as generating 5.1 channels, the last channel being dedicated to a low frequency subwoofer.) The program data from buffer  56  is fed via six lines L1-L6, to six processing channels. Typical processing circuits are shown in  FIG. 3  for one channel, it being understood that the elements for the other channels are substantially identical. 
   The program on L1 is fed first to a gain/phase circuit  58  for amplification, gain adjustment and phase correction in accordance with certain control signals as described below. 
   The adjusted signals are sent to a delay/reverberation circuit  60  where the delay of the signals for appropriate reverberation are adjusted. The signals are next sent to an equalizer  62 . After equalization, the signals are sent to a multiplexer  64 . 
   The operation of the multiplexer  64  is dependent on the number and arrangement of speakers that the costumer wants to use. For a full 5.1 channel surround sound, the multiplexer sends the signals to an appropriate speaker  66 , it being understood that similar speakers are provided for each of the other channels. 
   To achieve two channel ‘stereo sound’, the multiplexer  64  first sends the sounds for channel  1  to a mixer  68  on line m 1 . This mixer  68  also receives signals on lines m 2 , m 3  for signals from other channels. The signals from these channels are mixed at certain ratios described more fully below, to generate a ‘left’ signal for a speaker  70 . Similarly signals from lines m 3 , m 4 , m 5  generated by other channels (not shown) are fed to a second mixer  68 ′ where they are combined to generate a so-called ‘right’ signal for a speaker  70 ′. Thus, in effect, the two mixers  68 ,  68 ′ fold the signals from six channels into a standard two-channel stereo signals. 
   In addition, the playback apparatus  50  further includes a customer input interface  80  and a register  82 . The customer input interface  80  is used by the customer to input his preferences, and, if so desired, to override the AVCD as described more fully below. The register  82  is used by the manufacturer to store certain device specific information, such as whether the player is an automobile player, a home player, a personal or portable player, a studio player, and so on. 
   The acoustic characteristics of the playback site play an important role in the accuracy of the reproduction. These characteristics include the physical dimensions of the room where the playback apparatus is to be used, including characteristics of the walls, the location of the speakers, etc. For best reproduction quality, the playback apparatus  50  should have information descriptive of all these characteristics. 
   Two configurations are envisioned for providing these local characteristics to the playback apparatus  50 . In one configuration, an open loop control is used. In this configuration, the customer provides the descriptive information to the playback apparatus  50 . For example, in response to prompts, the customer may enter the size of the room, the location of the speakers, etc. This information is then stored in memory  83 . In addition, related acoustic parameters, are also determined and stored in memory  83 . 
   The information from memory  83  and register  82  is used by each of the elements  58 ,  60 ,  62 ,  64  in conjunction with the ACD information from buffer  54  to perform their respective functions. This feature of the invention is best explained in conjunction with a specific element.  FIG. 4  shows details of the delay circuit  60 . The delay circuit  60  includes a programmable delay line  91  and a control block  92 . The control block receives a reference delay parameter which is one of the parameters of the AVCD and is determined at the recording site  10 . The control block also receives an input from register  82 , or memory  83 . 
   Control block  92  may be for example a look-up table which uses the information received to generate an appropriate delay for the signals of channel  1 , by comparing for example the delay characteristic of the room with the optimal delay indicated by the reference delay parameter. This delay control signal is then fed to programmable delay line  91 . For example, the original performance may have been recorded in a concert hall having a delay time of 2 seconds. On the other hand the customer may be keeping his player in relatively small room with a delay of 0.5 seconds. Therefore for optimum playing a delay of 1.5 sec is required. This delay is developed by delay line  91  as defined by the control block  92 . 
   Of course, the customer may desire to have the sounds played with different characteristics. He may chose these characteristics using the customer interface  80 . When the customer makes his choice, rather then having the system generate the delay automatically, the customer choice is fed to the controller block  92  from memory  80  and is used to override any previous decisions. 
   Thus the operation of each of the elements  58 ,  60 ,  62 ,  64  is adjusted using information from the AVCD, the register  82 , memory  83  and the customer input interface  80 . 
   Of particular importance are the mixing ratios used by mixer  68 . As discussed above, these ratios can be set using information from the ACD which is derived from information on how the mixer  16  is set, and, optionally, the ratios set by the producer using keyboard  26 . 
   In the second configuration of the invention a closed loop control system is used. In this configuration, a control circuit  100  is provided which includes ( FIG. 5 ) a microphone  102 , an amplifier  104 , a processor  106 , and test generator  108 . The test generator is used to generate on command a test signal. For example, the test generator may be used to generate pink noise, or a particular test sound defined by the AVCD. This test signal is transmitted to the speakers of the player  50 . The test may be identical to the test signal from generator  22 . 
   Preferably the microphone  102  is located, at least temporarily, at a central location within the room wherever the customer prefers to listen to the player. The microphone  102  is connected via the amplifier  104  to the processor  106  either by direct wiring or by an indirect coupling such as RF, IR, or other similar means. 
   In any event, the processor  106  routes the test signals from generator  108  to each of the speakers  66  serially and/or simultaneously to allow the processor to analyze the acoustic characteristics of the customer&#39;s listening room, including its size, wall covering, speaker locations, and so on. Thus, instead of having the customer enter information and calculating these characteristics, the characteristics are obtained directly. These characteristics may have to be adjusted to compensate for changes in the room. 
   After the characteristics are obtained as described, they are stored in a memory  110 . The information from this memory is then used in the same manner as the information from memory  83 . Register  82  is still used to store player specific information. 
   The AVCD may be used for other important information as well. For instance, many high quality-players, especially players designed to be used in automobiles, may include a noise cancellation circuit for canceling road noise. Noise cancellation may be advantageously incorporated into the present system as follows. 
   Referring to  FIG. 6 , a noise cancellation circuit  140  includes a noise sensor  142 , a noise correction generator  144  and a mixer  146 . Sensor  142  is used to sense ambient sounds and it may be for example a local microphone. The noise signals thus sensed are fed to the noise correction generator  144 . The noise correction signal also receives from the AVCD information describing the spectral content of the program data on the corresponding channel, for example channel  1 . The noise correction generator  144  analyzes the sensed noise signals and generates noise compensation signals. In this manner, the noise correction generator  144  does not have to perform its own analysis to differentiate between the desirable sound signals and the undesirable noise signals. These compensation signals are added to the program signals by mixer  146 . Mixer  146  in turn mixes the channel  1  signals and the noise correction signals to thereby compensate for noise. 
   As previously mentioned, the AVCD may include metadata descriptive of the locations of the instruments, vocalists and/or recording microphones. This information is captured and displayed by a display  90  at the playback apparatus to give the customer a more accurate information about how the performance was recorded. 
   Although the invention has been described in terms of specific embodiments, it is intended that the patent cover equivalent substitutions for any of the elements of these embodiments, and that the protection afforded by this patent be determined by the legitimate scope of the following claims.