AC3 file losing sync -AC-3 Encoder - MAGIX Community Forums Archive

Subject:AC3 file losing sync Posted by: riredale Date:9/22/2002 12:20:54 PM When I make a vob from an elementary video stream and an AC-3 stream encoded from SoftEncode, the resulting vob shows the audio out of sync, and it appears to get worse further down the timeline. To make the AC-3 file, I first take my original avi and use VV3 to render out a wav file. This wav file is then fed into SoftEncode. Meanwhile, the original avi file is encoded into MPEG2 using the MainConcept encoder in VV3. What am I doing wrong? By the way, the complete vob file is about 3GB (about 1 hr) in length, and I understand that the official spec says that vobs should be no greater than 1GB. Still, I suspect I will still get an out-of-sync situation, even with a shorter vob.
Subject:RE: AC3 file losing sync Reply by: vonhosen Date:9/22/2002 4:26:11 PM How far out of sync are you going over what period of time ? Perhaps there are different frame rates used in the different encodes for the two files (one 30fps & one 29.97fps). This would lead to gradual loss of sync resulting in about 7 seconds out after 2 hours (if the maths is right).
Subject:RE: AC3 file losing sync Reply by: riredale Date:9/22/2002 11:14:29 PM The sync loss is about 0.5 sec after 24 minutes. This is less than what would be expected from the 30/29.97 ratio. I made a miniDV video of me clapping at the beginning, and about 24 minutes later. I then pulled the file into VV3, and noted the audio and video were in perfect sync. I used the MainConcept encoder in VV3 to convert the file to MPEG2 and MP2 elementary streams, which I then fed into a vob multiplexer (DVD Wise). Playing the vob with PowerDVD, I noted perfect sync at both points. Next I ripped the wav audio from the avi file, again using VV3. I then fed the wav file into SoftEncode, and I took the resulting ac3 file over to the vob multiplexer. Playing the new vob, I noted about a 0.5 second audio delay compared to the video at the 24-minute handclap point, but the handclap at the beginning was (nearly) in sync. Aaarrgh! I can shift the ac3 timing left or right, but of course either the beginning or the ending will be out of sync. I've tried various methods of ripping the wav audio from the video avi, including VirtualDub. Same results.
Subject:RE: AC3 file losing sync Reply by: riredale Date:9/26/2002 2:37:00 AM Okay, the problem was with the vob-creation routine built into DVD Wise. When I tried building a vob with other authoring programs, the audio was synched properly.

Subject:AC3 file losing sync

Posted by: riredale

Date:9/22/2002 12:20:54 PM

When I make a vob from an elementary video stream and an AC-3 stream encoded from SoftEncode, the resulting vob shows the audio out of sync, and it appears to get worse further down the timeline. To make the AC-3 file, I first take my original avi and use VV3 to render out a wav file. This wav file is then fed into SoftEncode. Meanwhile, the original avi file is encoded into MPEG2 using the MainConcept encoder in VV3.

What am I doing wrong? By the way, the complete vob file is about 3GB (about 1 hr) in length, and I understand that the official spec says that vobs should be no greater than 1GB. Still, I suspect I will still get an out-of-sync situation, even with a shorter vob.

Subject:RE: AC3 file losing sync

Reply by: vonhosen

Date:9/22/2002 4:26:11 PM

How far out of sync are you going over what period of time ?

Perhaps there are different frame rates used in the different encodes for the two files (one 30fps & one 29.97fps). This would lead to gradual loss of sync resulting in about 7 seconds out after 2 hours (if the maths is right).

Subject:RE: AC3 file losing sync

Reply by: riredale

Date:9/22/2002 11:14:29 PM

The sync loss is about 0.5 sec after 24 minutes. This is less than what would be expected from the 30/29.97 ratio. I made a miniDV video of me clapping at the beginning, and about 24 minutes later. I then pulled the file into VV3, and noted the audio and video were in perfect sync.

I used the MainConcept encoder in VV3 to convert the file to MPEG2 and MP2 elementary streams, which I then fed into a vob multiplexer (DVD Wise). Playing the vob with PowerDVD, I noted perfect sync at both points.

Next I ripped the wav audio from the avi file, again using VV3. I then fed the wav file into SoftEncode, and I took the resulting ac3 file over to the vob multiplexer. Playing the new vob, I noted about a 0.5 second audio delay compared to the video at the 24-minute handclap point, but the handclap at the beginning was (nearly) in sync. Aaarrgh!

I can shift the ac3 timing left or right, but of course either the beginning or the ending will be out of sync. I've tried various methods of ripping the wav audio from the video avi, including VirtualDub. Same results.

Subject:RE: AC3 file losing sync

Reply by: riredale

Date:9/26/2002 2:37:00 AM

Okay, the problem was with the vob-creation routine built into DVD Wise. When I tried building a vob with other authoring programs, the audio was synched properly.