AC3 quicker than video - Is there a non-reencoding solution?

[Spiny Norman]

It's possible the answer to the question (in bold) below is "no", but...

I had a video (25 FPS, see below) that was 1h13m while the video was 1h7m. Converting the audio to wav and stretching it did the trick. Somehow the audio had become sped up and there was no way to go back to the source and get a new copy. It's this xvid/avi file or nothing.

Now this adds a few conversion steps to the process so I was wondering: Would there have been a way to do this without re-encoding the audio?


File Name .........................................: TdL (1947).avi
File Size (in bytes) ............................: 1,563,989,018 bytes
Runtime ............................................: 1:13:45

Video Codec ...................................: XviD ISO MPEG-4
Frame Size ......................................: 720x576 (AR: 1.333)
FPS .................................................: 25.000
Video Bitrate ...................................: 2441 kb/s
Bits per Pixel ...................................: 0.235 bpp
B-VOP, N-VOP, QPel, GMC.............: [B-VOP], [], [], []

Audio Codec ...................................: 0x2000 (Dolby AC3) AC3
Sample Rate ...................................: 48000 Hz
Audio Bitrate ...................................: 384 kb/s [2 channel(s)] CBR
No. of audio streams .......................: 1

[jagabo]

Change the frame rate of the video with a program like AviFrate.

[Spiny Norman]

Change the frame rate of the video with a program like AviFrate.

Yeah, I tried that, and it worked, but then I have a video with a 27.something frame rate. So that would mean sound AND picture are going faster than they should.

[poisondeathray]

For playback, you can use the audio "stretch by" option in MKVToolNix if you re-wrap in an mkv container. But the quality usually isn't the best since it's done on the fly in realtime, you can get crackles

[jagabo]

Some containers, like MVK, let you specify a stretch/shrink factor for the audio. Unfortunately, not all players will obey the flag.

[Spiny Norman]

For playback, you can use the audio "stretch by" option in MKVToolNix if you re-wrap in an mkv container. But the quality usually isn't the best since it's done on the fly in realtime, you can get crackles

Some containers, like MVK, let you specify a stretch/shrink factor for the audio. Unfortunately, not all players will obey the flag.

So you're both saying that that is not the best solution, right?

[poisondeathray]

So you're both saying that that is not the best solution, right?

Yes. Re-encoding is better because it's compatible everywhere, yields higher quality results

[hello_hello]

It's either re-encode the audio or change the frame rate. Try opening the AVI with VirtualDub. It has an option to change the frame rate to match the audio duration. That may do the trick, or you may need to adjust it manually until it's right. Once you're done, save it as a new AVI after selecting "direct stream copy" as the video compression method under the Video menu (no re-encoding). The audio should default to direct stream copy.

[Spiny Norman]

It's either re-encode the audio or change the frame rate. Try opening the AVI with VirtualDub. It has an option to change the frame rate to match the audio duration. That may do the trick, or you may need to adjust it manually until it's right. Once you're done, save it as a new AVI after selecting "direct stream copy" as the video compression method under the Video menu (no re-encoding). The audio should default to direct stream copy.

This was suggested before, and what I wanted to know was if I could somehow do the opposite, because a 27.something frame rate just seems wrong.

[hogger129]

+1 for MKVToolNix. You can add a delay to it to bring it back into sync and it just puts it back into another .mkv container.

[hello_hello]

It's either re-encode the audio or change the frame rate. Try opening the AVI with VirtualDub. It has an option to change the frame rate to match the audio duration. That may do the trick, or you may need to adjust it manually until it's right. Once you're done, save it as a new AVI after selecting "direct stream copy" as the video compression method under the Video menu (no re-encoding). The audio should default to direct stream copy.

This was suggested before, and what I wanted to know was if I could somehow do the opposite, because a 27.something frame rate just seems wrong.

Sorry. I must have missed that post.
I'd be re-encoding the audio. Yes, you can stretch it with MKVMergeGUI if you don't mind remuxing it as an MKV but it tends to make decoding it properly (no pops or crackles) a bit hit and miss if it's stretched by anything other than a very small amount. Better to stretch it while re-encoding, even if in theory there is some quality loss.

[Spiny Norman]

Thanks for the input. Seems to be just as I feared. Well, there is some re-encoding that shouldn't have been necessary, but the damage is minimal.