demux quality

[trinidav]

Is there a free program that will demux the video to a valid elementary stream, without reencoding, and that is 100% the same quality as the original?

What I'm trying to do is to take a non-reencoded demuxed m2v stream, that is capable of working correctly in a video editing program, and add sound effects, different dialogues, and different soundtracks. Sync is very important.

Since the video portion does not need to be changed, I would like to keep the original quality of the demuxed stream, and simply add sounds.

I have tried using a demuxed m2v stream from DGMPGDec, but find that the stream will not sync properly, at least in the editor I'm using. I can take that stream and reencode using tmpgenc, but that is what I'm trying to avoid, which is reencoding. And I may not be using DGMPGDec for it's intended purpose. It's a great program.

[Guest]

Once you demux to elementary streams you lose the information that syncs them. Elementary streams do not carry timestamps. You have to do the sync manually then. This is just a fact of life.

[mpucoder]

Demultiplexers give you back the elementary streams that the original authoring program used. There is no quality lose, the output will be bit-for-bit identical.
I have to differ with Neuron2, though, about timestamps. Mpeg video does carry a timestamp in the GOP header, and it can and usually is different from the timecodes of the multiplexed product. For movies which were telecined in one continous process the code, at "video start" will usually be 01:00:00:00. The reason it is a full hour ahead is that negative numbers are not allowed, and telecining usually starts 5 seconds or so before "video start". Movies with independantly telecined segments, compilations of videos, and live video edited down will contain a mixture of mostly meaningless timecodes. In authoring programs like Scenarist the start time, called "start time to video", can be very annoying to get the right value.

You didn't say what editor you are using, but most have the option to either sync the audio to a certain time in the video or to ignore the video timestamp.

[Guest]

I stand corrected. But what about the audio, which has no GOPs? Since the OP was asking about sync, he still loses the possibility of getting automatic sync and will have to do it manually.

[mpucoder]

Some audio formats can contain timestamps, but these are either not acceptable for DVD or the timecode is removed during multiplexing. For example AC3 may contain an embedded timecode, but I have never seen it used for DVD. AC3 can also use an external timecode in a wrapper, but that is discarded during muxing. So, afaik, there are no timecodes in any demultiplexed audio.

However, if the video timecode is not 00:00:00:00 some editors skew the sound. I don't know which editor is being used, but three solutions are:
1) in the editor set the audio start time to match the video start time
2) have the editor ignore video timecodes
3) reset the video timecode to 00:00:00:00 with a patcher such as ReStream

Re-encoding sets the timecode to 00:00:00:00, and trinidav implied that worked, so resetting the timecode should also work.
There still could be sync problems caused by audio gaps or still frames (you lose that information when demuxing). As for audio delay, I've posted elsewhere many times about it being the result of improper demuxing, that in reality no DVD has any audio delay.

[setarip_old]

@trinidav

Hi!Is there a free program that will demux the video to a valid elementary streamI can take that stream and reencode using tmpgencSince you have TMPGEnc, is there a reason you're not using it to demultiplex? (TMPGEnc>>File>>MPEGTools>>Demultiplex)

[trinidav]

@trinidav

Hi!Since you have TMPGEnc, is there a reason you're not using it to demultiplex? (TMPGEnc>>File>>MPEGTools>>Demultiplex)

As far as I can tell, TMPGEnc will not import a vob file for demuxing.

Is there a non-linear editor that works with video streams demuxed straight from vobs?

If the demuxed film stream is imported to a NTSC 29.97 project, playback is jerky, jumps around, and the timeline is not correct. If the same stream is imported to a 23.97 project, playback is not jerky but the timeline is also not correct. Maybe I'm missing a playback setting or import setting, although I've tried just about every combination.

I've tried running it through restream first, but it did not seem to make a difference.

Maybe this is all user error, but I'm beginning to think that wanting to import a demuxed video stream straight from a vob, into a NLE, is not typical.

[setarip_old]

As far as I can tell, TMPGEnc will not import a vob file for demuxing.It will. After TMPGEnc>>File>>MPEGTools>>Demultiplex, select "Browse" and then change (click downarrow) "Select "File of type" to "All files"...