Damaged Audio, Need help...

[Darkwhisperer]

Hi,

I have an AVI file, & the audio is damaged. As an AVI, the audio works fine, and is in sync with the video. But Im trying to convert the AVI to DVD. I exctract the audio, using Virtualdub, & try converting it to MP2 for TMPGEnc using BeLight. But its reports problems with certain parts of the wav file, & so the audio ends up short of the video.

Is there some app. that, upon having errors with a certain part of an audio file, will insert some kind of blank sound in its place? Can this even be done? If not, please can someone explain why not?

Your help is kindly appreciated... :thanks:

[tebasuna51]

Original audio: ac3 or mp3?

To extract audio from avi use VirtualDubMod -> Streams -> Stream List -> Demux

Try DelayCut (http://jsoto.posunplugged.com/audiotools.htm) to insert silence in bad CRC frames.

[Darkwhisperer]

Im reasonably sure its VBR-MP3. but I'll try DelayCut tonight and see how it goes... Thanks alot tebasuna51. Really appreciate it.

[tebasuna51]

If you use VirtualDub to extract a mp3 VBR is sure your audio is damaged.

Instead use VirtualDubMod -> Streams -> Stream List -> Demux. Answer "No" to the question: "Do you still want to rewrite the header?"

[Darkwhisperer]

Alright, I'll try the VirtualDubMod demux. But I get errors when Im converting the WAV to MP2 using BeLight. In different places, not just the beginning or end. Will try this tonight, & let you guys know the result.

[tebasuna51]

What WAV?. A PCM WAV can't contain errors, maybe bad sound but not errors.
If you have a avi with mp3 VBR and use VirtualDubMod demux you get a MP3 VBR.
If you need more help, please, put the log of Belight conversion.

[Darkwhisperer]

Well, what I had done was use VirtualDub's File -> Save Wav function. I'll put up the BeSweet log tomorrow.

[setarip_old]

@Darkwhisperer

It would be beneficial to know what your original .AVI contains:

1) Load the original video file into VirtualDub (or one of its many variants) or NanDub

2) From the "File" dropdown menu, select "File Information"

3) Post (here) EVERYTHING you see (BOTH video and audio information), or post a screen capture .jpg of the information box

[Darkwhisperer]

Hi guys...

The DEMUX with Virtualdubmod worked. tebasuna51, you rock. Thanks to all for your help.

Thanks for having such a great forum... :-D

[Darkwhisperer]

Well, it DIDNT work. :-/

I DEMUXed as requested. Gave me an ac3 file. Then I loaded the AVI into TMPGEnc 3.0 Express, replaced the AVI audio with the AC3 file, & presto! In the preview, the sound is perfectly in sync till the end. So I let TMPGEnc do its thing. Then, I check the resultant MPEG file this morning. The sound is gone off.

I didnt have any time to check what went wrong or where. Tho anyone have any ideas why this would have happened? Also, please ask for any details that your'll need, & I'll bring it in tomorrow.

[setarip_old]

You can resynch the MPEG file as follows:

1) Load it into TMPGEnc

2) From under the "Advanced" tab, put a checkmark next to and then double click on "Source Range"

3) Enter an appropriate positive or negative amount of milleseconds (thousandths of a second) next to "Audio gap correct"

4) Save with a new filename

Let us know of your success ;>}

[Darkwhisperer]

How would I calculate what amount to use for the gap?
Also, the sound is fine for most of the 1st half. But then it went off somewhere...

Will try it tho, & let your'll know.

[tebasuna51]

Well, we have ac3 instead mp3 vbr. There are two common problems in ac3 streams to be used with authoring software or TMPEGEnc (works fine with avi players):

- Leading zeroes to implement a delay. If "the sound is fine for most of the 1st half" and is synchronized, isn't your problem.

- Bad ac3 frames inside the stream (CRC errors). Then you must correct the ac3 stream before use authoring software or TMPEGEnc. You can try DelayCut (http://jsoto.posunplugged.com/audiotools.htm) to fix the ac3.

[Darkwhisperer]

I think its bad frames. I got multiple CRC errors when I was converting the file to MP2 with BeSweet. Havent had a chance to play with it, but I definitely will try DelayCut tonight. I assume I must use "silence" as the setting for CRC Errors in DelayCut?

[tebasuna51]

If there are many frames with CRC errors you must use "Fix" or "Silence", with "Skip" you can lose sync, and "Ignore" does nothing.

You can try "Fix" sometimes is less noticeable than "Silence".

[Darkwhisperer]

Cool. Thanks :-)

[Darkwhisperer]

Well, it seems there are LOTS of damaged frames. Delaycut loses about 90 seconds, whether I use fix or silence. *SIGH* Any other ideas?

[setarip_old]

Since you seem to be at a dead end trying to use the .AC3 audiostream, try the following as an experimental first step instead:

1) Load the original .AVI into VirtualDubMOD
2) Set "Video" to "Direct Stream Copy"
3) Rightclick on the .AC3 audiostream (Under the "Streams" dropdown menu) and choose an appropriate 48,000Hz .MP3 audio bitrate (192Kbps should be good)
4) Save with a new filename
5) Use this new file as input for "TMPGEnc Express"

[Darkwhisperer]

Thats an idea... I'll try it tonight.

[Darkwhisperer]

Well, when I tried setarip_old's idea, I got an "Unable to decode audio..." Something along those lines...

Anyway, what I did was the following:

(1) File -> Save as Wav... in VirtualDub.
(2) Converted the "wav" to mp3 in Belight. In the log, wherever it reported a CRC error, I deleted that from the original video, both video & audio.

I went through that about 5 times, bcos errors kept appearing in the log.

In the end, I lost about 60 seconds of video, but the audio stayed in sync. Half the errors were in the credits, which I chopped out altogether.

Thanks for all your help & co-operation :-D