I've been looking into this in the last few days. And I believe it might be possible but it's rather unusual like Ross said. The DVD specification has a private stream definition in a Mpeg2 program stream that allow LPCM. I have been successful to have standard player like VLC to play a Mpeg2 program stream that has LPCM wrapped around a private ES with LPCM.
However like Ross said when you try to wrap LPCM into a transport stream you run into trouble. From my own investigation I have found this is not because the ISO/IEC 13818-1 don't have provision for it. It is mostly because nobody seems to do it outside of special broadcasting purpose. Also there is some confusion about how to do it. Yet I have been successful to use Live555 without any modification to experiment and create a compliant Mpeg-2 transport stream that has LPCM wrapped into a private stream. To experiment with that feature you only need to create with Elecard Pro Muxer a Mpeg2 program stream that has Mpeg2 video ES and LPCM audio which is DVD compliant. Then use the testing application testMPEG1or2ProgramToTransportStream to create the Mpeg2 transport stream with LPCM wrapped into a private stream. However when you try to play the transport stream into a standard player like VLC Media Player the audio is not recognized. I have investigated the issue with VLC Media player. Strangely VLC media player has provision to demux the LPCM audio from a Mpeg2 transport stream. I checked the code. However there is a bug in the code that prevent VLC to properly recognize the LPCM audio stream. Only a small modification would be needed to have VLC Media recognize the LPCM audio private stream. I posted on VLC developer email list a request for investigation of the issue but I have had no reply. Thought it is off topic on this list I include a copy of the email I sent to the VLC developer list for academic purpose. Here it is: VLC Developer posting I have tried to decode a LPCM DVD like compliant audio stream with VLC Media player inside an Mpeg2 program stream. And VLC Media Player nicely recognized the audio stream and played it as well as the accompanied Mpeg2 Video stream in the Mpeg2 program stream. I used LiveMedia testMPEG1or2ProgramToTransportStream.cpp testing application to create a transport stream wrapping the Mpeg2 DVD like program stream. Using an Mpeg2 Stream Analyzer from Elecard I was able to find that LiveMedia created the properly Mpeg2 Transport stream around the program stream. I have tried to playback the created Mpeg2 Transport Stream with VLC and though the video played nicely the audio wasn't decoded. I Opened the Message Dialog Box of VLC and found that the LPCM Audio Codec wasn't instantiated this time. I downloaded VLC source code and began investigating the problem. I checked through the file "ts.c" trying to find what going on. I quickly found the code where the private type 0x06 of the packetized elementary stream is checked to find what data is carried. My understanding of the code is that LPCM audio is detected inside a private stream when the Mpeg-2 descriptor is matched with "BSSD" (Line 2961 of ts.c). Now looking at the Website: http://www.smpte-ra.org/mpegreg/mpegreg.html http://www.smpte-ra.org/mpegreg/bssd.html I found that BSSD is associated to the mapping of audio data as specified in SMPTE Standard SMPTE 302M-1998 for Television which is "Mapping of AES3 Data into MPEG-2 Transport Stream". This is a LPCM audio stream formatted according to AES3. I have found that LiveMedia doesn't add the descriptor when wrapping the transport stream. Then for sure the audio will never be recognized. Now will adding the BSSD descriptor solve the problem? Well I did not try it but I expect it will properly decode the audio stream. However when doing that I will create an improperly association between the audio data and the BSSD descriptor and thus have an illegal Mpeg2 Transport Stream that won't be recognized by other decoder. Why ? Because the BSSD description create an association with an audio AES3 formatted LPCM P-ES stream. Not a DVD-Video audio LPCM formatted P-ES. They do not share the same formatting. The LPCM audio codec "lpcm.c" used by VLC is clearly a formatted DVD-Video audio LPCM codec. Not an AES3 LPCM formatted audio codec. I suspect that the descriptor to be used to create the properly association is: "DVDF". Please check: http://www.smpte-ra.org/mpegreg/dvdf.html Unfortunately I do not have any stream sample of a DVDF Mpeg-2 transports stream to double check my finding. But I believe this is an issue that will prevent the decoding of a compliant DVDF Mpeg-2 transport stream. Anyone having a DVDF compliant stream could confirm my finding please ? Guy -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ross Finlayson Sent: Tuesday, January 29, 2008 12:28 AM To: LIVE555 Streaming Media - development & use Subject: Re: [Live-devel] Mpeg Audio missing or corrupted in MPEG-2 Transport Stream or seperate sreams >Where should I look to figure out what I need to do to possibly stream >mpeg2 video and pcm audio in a transport stream? I don't believe that PCM audio can be included in a Transport Stream (at least, not in any standard way that a receiver is likely to understand). Ross Finlayson Live Networks, Inc. (LIVE555.COM) <http://www.live555.com/> _______________________________________________ live-devel mailing list live-devel@lists.live555.com http://lists.live555.com/mailman/listinfo/live-devel _______________________________________________ live-devel mailing list live-devel@lists.live555.com http://lists.live555.com/mailman/listinfo/live-devel
