Muxing problems with TMPGenc

[iks]

Hi,
I have got problems with some mpeg1 files. If I demux them and mux them again, the audio is out of sync. :confused: The original file plays ok. Does anyone have an idea, why this happens?

[barakori]

Hi,

I had a related problem, and the way I solved it might be useful in your situation.

I wanted to put VCD content on DVD. For that, I had to convert the audio to 48KHz (either MP2 or AC3). My original thought was to dumux and use BeSweet (+SSRC) to convert to 48KHz audio.

It turned out the audio was out of sync. Sometimes by 5 seconds for a 40 minute video. I used VirtualDub and saw it's also off by the same 5 seconds. I muxed the demuxed streams, and indeed, the 5 second async was there.

I was that Media Player (and other software DVD players) showed the original movie properly (buy not the muxed one). So somehow, the content in the audio stream is affected by the video stream, and once you demux them, the information is lost. I don't know what's that information (If someone knows, please tell us...)

My solution was to demux the original MPEG1 (VCD) file, but not to use the audio track. Instead, I used TMpgEnc to extract the audio track and encode it as MP2 (Use audio only stream). I was using the "DirectShow Multimedia File Reader" as the VFAPI plun-in with the highest priority (Options -> Environmental Settings), since this is what Media Player uses.

I also used SSRC as the external tool for sample rate changes (Options -> Environmental Settings -> External tool) since a lot of people suggested it does better job than TMpegEnc's internal sample rate converter. Also, I used DVD audio charasteristics (48Khz, MP2, 384Kbps). In your case, maybe sample rate conversion is not required.

Just as a side note, I still got a small a async problem in the result DVD, which was fixed when I added a last step to encode the audio to AC3 using BeSweet. It seems that DVD players handle AC3 better.

I know some quality must be lost on the way, but I actually couldn't notice anything. Of course, if I had to choose between some loss of quality and audio asynch of 0.2 sec over 40 minutes of video, I would choose the former.

Hope it helps,

Barak