Refresher on Linear PCM and TMPGEnc / MPEG-2, please!

[Bizuser]

As I get older, my memory fades ... I try to make copious notes to compensate, but I can't always find them . Google usually helps me out, but on this one, I'm getting nowhere.

I've done all manner of conversions over the years ... PAL->NTSC, VHS captures, etc but one I'm working on today is stumping me! I'm working on a new machine, so I'm guessing this is just a matter of some configuration setting I need to set once and forget in TMPGEnc. I've answered this before, I know.

Basically, as a result of prior steps, I have an .MV2 video file (MPEG-2 video) and a .WAV audio file (linear PCM). I'm trying to multiplex them in TMPGEnc, and I get the error "Linear PCM stream can not be outputted as system stream". The thing is, I have created numerous MPEG-2 files with TMPGEnc that use Linear PCM ... I have notes about setting the audio bitrate at 1536, for example. I can fix this by changing audio setting to MPEG-1 Audio Layer II (and have done to get this particular project completed) but ... it's just bugging me that I can't set PCM since I KNOW I've done it in the past.

So what's the scoop with TMPGEnc, Linear PCM audio, and MPEG-2 files? Again ... I KNOW I've created MPEG-2 files using TMPGEnc with PCM Audio - and they play fine after authoring to DVD on my set-top players.

Any insight greatly appreciated!

[jman98]

What's the bit rate of video files? There's an upper limit to what the muxed video+audio bit rates can be. If your peak video bit rate ever gets above 8500 Kpbs, TMPGenc may actually be telling you in a very very bad way that the real problem is that the video+audio (remember, PCM is around 1500 Kbps) is too high for DVD standards.

[Bizuser]

Well ... I think I was wrong ... or at least, could very well be! Looking back through my notes and folders in more detail (it's been a year since I last did this particular type of stuff), I see now that I used TMPGEnc DVD Author to author the final DVDs, and I was using it to pull together m2v and wav files ... so ... it could be that TMPGEnc itself has the restriction that it won't generate an MPEG-2 file with linear PCM Audio, but yet TMPGEnc DVD Author can multiplex a PCM Wav file into a final DVD.

Since both products come from the same vendor, that's a surprise, but .... maybe that's just the way it is!

So is it true ... TMPGEnc (the video encoder) cannot produce an MPEG-2 system file with linear PCM audio, while TMPGEnc DVD Author can produce a DVD with linear PCM audio? Is this a standards issue or a TMPGEnc issue?

To answer your last question, no the bitrate is very low so that's not the issue.

[Cornucopia]

#1 DVD specs say that the highest AUDIO bitrate allowed is (IIRC) 6144kbps, so NO 1536 isn't too high.

#2 TMPGEnc isn't being inconsistent:
All standard MPEG2 program stream muxers CAN'T mux in LPCM audio--they're not allowed. I think it probably has something to do with not having any internal timecode (talking raw PCM here, not WAV or AIF as the internal PCM is what's actually used, not the container).
VOB's are a SUPERSET or variant of MPEG2 Program streams, where the component elements are stored in PES's. So, muxer's that create VOB's (usually only DVD Authoring apps) are the only ones that can use PCM audio as a source.

Scott

[redwudz]

You mention you are trying to multiplex the WAV to the M2V video? It should accept the WAV for conversion to MPEG-1 Layer2 audio. Don't know that I have every tried to mux them with a M2V video in TMPGEnc.

But I never use TMPGEnc to encode a WAV file to MP2. I drop the WAV into ffmpeggui and convert to AC3 and use that with TMPGEnc DVD Author for the audio. But if you are looking for the best quality audio, probably using the WAV to author with should work well enough. I don't usually have that much free space on my DVDs to use WAV audio.

EDIT: I like Cornucopia's answer better.

[Bizuser]

Thanks to everyone for the insight and corrections. I understand the answer given by Cornucopia and it makes perfect sense. I have been away from conversions and authoring for about a year and it's amazing what you forget!

I have, historically, avoided too many intermediate steps, especially demuxing, processing and re-muxing, because of the risk of introducing sync problems - audio-video (lip synch) issues. But I will try the ac3 conversion step mentioned above as it sounds good. I have used besweet in the past; very powerful but complicated for quick projects.

Thanks again!