Log in

View Full Version : VCD2DVD: Captured MPEG1 file with padding stream & the audio sync problem !!!


Digimax
6th October 2003, 10:49
Hi!

I have a very strange problem, and as I found out during my extensive searches during the past few days, lot's of other people have the same problem, and no sollution can be found.

It is about TV show captures in MPEG-1 for VCDs, which can not be transcoded to any other format (like for DVD), because trying it, the audio gets badly out of sync.

What I found out so far:

It has to do with a PADDING STREAM, which can be found in such MPEG-1 files besides the video and audio stream.

As everybody should know, to be able to use a VCD-file on a DVD, just the audio has to be transcoded from 44.1 kHz to 48 kHz, which is done by demuxing the stream, transcoding the audio, and remuxing it again.

But this doesn't work, because demuxing the stream get's rid of this padding stream, which is then missing when remuxing it again, and the missing padding stream causes the audio getting out of sync very badly.

Using TMPGEnc: When doing a simple demux, nothing strange will be found, but the normal demux option in the MPEG tools shows the presence of this padding stream, which also can be extracted (gave a file of about 300kB for a TV show with a length of about 30 minutes during my tests), but not be reused with muxing the stream again (TMPGEnc doesn't accept the selection of the padding stream, only video and audio).

I found several info, what other's tried to solve this problem, like stretching the audio, using M2-Edit (which I tried, but could not get to do something usefull to the MPEG1-file however), but they are pretty complicated, take a lot of time, and do not leed to a 100% clean sollution.

I think, if it is really common, that such a padding stream is used in MPEG-1 files, there should be software available capable of handling this stream. All I want to have done, is to transcode the audio of such a file from 44.1 to 48 kHz without the padding stream to get lost.

There has to be something out there.

None of the usual encoding & authoring programms, like TMPGEnc Plus, TMPG DVD Author, InterVideo WinDVD Creator 2, DVD-Lab... can be used, they all simply ignore the padding stream and produce out of sync results.

So what can be done ???

I am looking for a really simple sollution, so no playing arround with audio stretching, as it would be much too much work for my purpose. I just want to store my favorit TV shows, which I download over the internet (and which are most commonly in this MPEG-1 format with padding stream), on DVD-Rs to be able to play them in a standalone Sony DVD-player.

BTW Can somebody explain the exact purpose of this padding stream, and why it is being ignored by all the software I have mentioned ???

Sincerely,
DigiMax

Digimax
7th October 2003, 07:57
Noone any idea ?????

I did some more tests yesterday transcoding my testfile with the DivX 5.1 codec using Xmpeg 5.0, and the resulting AVI-file was absolut fine, so audio and video were perfectly in sync like the original MPEG1-file.

So I assume DivX deals quite right with this padding stream, because it will have to use it somehow, as audio and video get transcoded.

But why the hell it makes that damned problems transcoding such a file to a DVD compatible format ???

sh134
13th October 2003, 12:59
I'm trying to resolve the exact same problem without success. I've tried converting to VCD2.0 (VCDEASY) and using the dat file in the hope that the autopadding that VCDEASY does is retained.

TMPGenc DVD Author 1.5 recognises the dat file and encodes OK. This is better than encoding the mpeg direct, but the synch problem resurfaces after about 20-25 minutes instead of the usual 2min.

I'm wondering if this is because of the audio encode freq (41.1kHz) on the mpegs I'm using. I've tried rencoding to 48kHz using TMPGenc 2.5, but remultiplexing the audio & video seems to make the problem worse in the source mpeg.

I'm still experimenting because no-one out there seems to have a foolproof method, and I'll post any further progress I make.

Regards

sh134
13th October 2003, 15:47
Sorry getting my projects mixed up, when I said dat file I meant the MPG (AVSEQ01.MPG), but I'm sure you realised that!

sh134
17th October 2003, 11:40
Tried using MainConcept mpeg encoder on the VCDEasy dat file (mpeg1 - AVSEQ01.DAT) to change the audio sample rate to 48kHz. This also screws up the sync.

The best so far has been writing the VCDEasy dat file using TMPGenc DVD Author (20-25min before sync goes).

Any other suggestions (from anywhere!) would be appreciated.

Stuart