Audio sync issue decoding transport stream

absinthe · 3rd March 2005, 15:17

I'm new to transport streams.

I've selected the audio and video PIDs, and saved the project as usual. However, after converting the video to XviD and muxing in the AC3, it starts out in sync but gets out of sync toward the end. I'm not really sure yet if it's gradual or all at once.

When I first opened the TS, I was warned that the the first GOP was not closed and that the first few frames might not be decoded correctly (just in case that info helps).

I should mention that in the process of correcting the audio delay (as indicated in the file's title, i.e DELAY -420 ms), ACDelayCorrector said the file was damaged. So I ran the file through ACFix and was then able to correct the delay.

Further, I also gave a try to changing the AC3 to Mp3. I did this by letting DGIndex decode to wav, during which process DGIndex indicated an "audio error." However, after muxing the Mp3 in with the XviD, it seems to go out of sync in the same way it did with the Mp3.

When I watch the TS in VideoLan, it plays in perfect sync.

Ideers?

-abs

absinthe · 3rd March 2005, 22:15

Nada? Is it something I've done wrong?

Guest · 3rd March 2005, 22:38

Let's not open this can of worms again, please.

DGMPGDec is not designed to recover missing audio or video, as results from errored transport streams. Maybe one day, but not now. For crappy streams, there is ProjectX, etc.

AC3Fix has been known to destroy AC3 files, ruining sync. Try it without the AC3Fix and see if things are better. And don't use AC3DelayCorrector either. Just make the offset in VirtualDub, or your MPEG encoder.

absinthe · 3rd March 2005, 23:07

So, then I'm probably not doing something wrong. Damaged stream, I reckon.

Guess I'll just have to ...

... "play it by ear"

Trahald · 4th March 2005, 20:50

delay_cut (by jsoto) may fix the stream.. it inserts silence in damaged areas... might be worth a shot. ive used it on some ac3s and the results had perfect sync.

absinthe · 7th March 2005, 14:11

Thanks for the tips! BTW, I took neuron2's advice and looked into ProjectX. All I did was open the TS file and demultiplex with default settings. I recreated my *.d2v file from the demuxed MPG2 stream and used the demuxed Ac3, and sure enough it's perfect

Very nice little program.

-abs

3rd March 2005, 15:17	#1 \| Link
absinthe Registered User Join Date: Aug 2004 Location: North Carolina, USA Posts: 270	Audio sync issue decoding transport stream I'm new to transport streams. I've selected the audio and video PIDs, and saved the project as usual. However, after converting the video to XviD and muxing in the AC3, it starts out in sync but gets out of sync toward the end. I'm not really sure yet if it's gradual or all at once. When I first opened the TS, I was warned that the the first GOP was not closed and that the first few frames might not be decoded correctly (just in case that info helps). I should mention that in the process of correcting the audio delay (as indicated in the file's title, i.e DELAY -420 ms), ACDelayCorrector said the file was damaged. So I ran the file through ACFix and was then able to correct the delay. Further, I also gave a try to changing the AC3 to Mp3. I did this by letting DGIndex decode to wav, during which process DGIndex indicated an "audio error." However, after muxing the Mp3 in with the XviD, it seems to go out of sync in the same way it did with the Mp3. When I watch the TS in VideoLan, it plays in perfect sync. Ideers? -abs __________________ The perfect browser is now completely free: Opera. Get it. Love it.

3rd March 2005, 22:15	#2 \| Link
absinthe Registered User Join Date: Aug 2004 Location: North Carolina, USA Posts: 270	Nada? Is it something I've done wrong? __________________ The perfect browser is now completely free: Opera. Get it. Love it.

3rd March 2005, 23:07	#4 \| Link
absinthe Registered User Join Date: Aug 2004 Location: North Carolina, USA Posts: 270	So, then I'm probably not doing something wrong. Damaged stream, I reckon. Guess I'll just have to ... ... "play it by ear" __________________ The perfect browser is now completely free: Opera. Get it. Love it.

4th March 2005, 20:50	#5 \| Link
Trahald Wewkiee Join Date: Feb 2002 Location: kashyyyk Posts: 2,269	delay_cut (by jsoto) may fix the stream.. it inserts silence in damaged areas... might be worth a shot. ive used it on some ac3s and the results had perfect sync. __________________ ...yeah...but...why on earth would I compare apples with apples?

7th March 2005, 14:11	#6 \| Link
absinthe Registered User Join Date: Aug 2004 Location: North Carolina, USA Posts: 270	Thanks for the tips! BTW, I took neuron2's advice and looked into ProjectX. All I did was open the TS file and demultiplex with default settings. I recreated my .d2v file from the demuxed MPG2 stream and used the demuxed Ac3, and sure enough it's perfect Very nice little program. -abs __________________ The perfect browser is now completely free: Opera. Get it. Love it.*

3rd March 2005, 22:38	#3 \| Link
Guest Guest Join Date: Jan 2002 Posts: 21,901	Let's not open this can of worms again, please. DGMPGDec is not designed to recover missing audio or video, as results from errored transport streams. Maybe one day, but not now. For crappy streams, there is ProjectX, etc. AC3Fix has been known to destroy AC3 files, ruining sync. Try it without the AC3Fix and see if things are better. And don't use AC3DelayCorrector either. Just make the offset in VirtualDub, or your MPEG encoder.