Audio Dropout in Nandub for DivX

[megamachine]

After using Nandub to combine a DivX encoded AVI file and an MP3 file, I found that the audio drops out about half way through. The separate AVI and MP3 files play fully till the end, but in combing them in Nandub I lose the audio about half way through. I have used the same procedure in Nandub for several projects and this has never happened before. The only thing that differs in this project is that the original source was captured from a VHS rather than DVD, and at the point where the audio drops out there is rolling frame in the video. Could that be it? Could the rolling frame somehow throw off the time? If so, how can I fix it? Or, is there possibly a problem in the way I am using Nandub? Many thanks for your time and kind assistance, with best wishes.

[megamachine]

By the way, attached is the File Information from NanDub.

[setarip]

Try loading it into either VirtualDub 1.5.4 or VirtualDubMod. Set BOTH "Video" and "Audio" to "Direct Stream Copy". Scan for bad frames. Save with a new filename...

[megamachine]

Thanks for the advice. I tried loading the final encoded AVI file into both VirtualDub and VirtualDubMod, as per your suggestions. At first, I got a message saying the file had "an improper VBR audio encoding" and recommended changing the audio header to CBR, but warning that sync would be offset. So, I made copies of the file and tried multiple permutations, with or without the CBR switch, and each time scanning for bad frames, with VDub set to direct stream copy mode for both audio and video. On the scans, no bad frames were detected, so I saved the files with new names but the problem persisted. On the ones switched to CBR, the audio was severely out of sync, as warned, but in both cases the audio drops out at precisely the same spot, about half way through. I double checked the original VOB file, made from an MPEG-2, and the audio/video both work fine, as they do in the demuxed audio and video streams. It is only in re-combining them in VirtualDub after separate compression that the audio dropout problem appears. Is there something else I can try? I want to understand and fix this problem, since I hope to be able to replicate my (hopefully) successs in subsequent projects. With many humble thanks for your very kind assistance. Best wishes.

[megamachine]

Other than bad frames, could there be any other reasons why I might be getting this audio dropout? Is there a guide some one can recommend to walk me through VHS (with external capture device) to DivX or XviD? I have been using a guide for DVD to DivX, and it works perfectly from DVD, but wonder if there may be any differences in the settings when capturing from a VHS source.

[The Edge]

Strange one alright.

Download Graphedit and register it. Drag the movie into it and play the problem file. Also see what Directshow filters are listed. Then report back here. Post a screenshot if ypu can.

Edge

[megamachine]

Thanks. I loaded the DivX encoded file with the audio dropout into GraphEdit and played it. It behaves the same way, the audio drops out about half way through. I took a screen shot of GraphEdit with the Graph Statistics window open. I'm not sure if this is exactly what you were looking for, so let me know if you need more, or if there is something else I can try to salvage this.

[megamachine]

I've been experimenting with short clips to try and solve this problem, to avoid the long wait time for encoding, and found something that might explain the problem. Here's what I did:

-Capture PAL VHS as MPEG-2 at 3mbs with MPEG-1 48khz audio
-Trim the file with MPEG2CUT, with that resulting in a VOB file that plays fine with PowerDVD
-Use DVD2AVI to demux the file into .d2v and .mpa streams, with the resulting .mpa file playing normally until the end
-Follow usual procedure for DivX encoding of the video stream, using VFAPI and VirtualDub, with 2-pass DivX encoding at 650kbs

So far so good, now the next step is to use Headac3he to compress the audio stream to .mp3, which gave me a problem.

In Headac3he, after setting it the way I usually do, and hitting start, I got an error message that says "Read less bytes than expected." Not sure what to do, I first experimented with using VBR, ABR or CBR, but that seemed not to matter, so I went to the the section in Headac3he that allows setting the frame range for encoding, which in its default setting is turned off, and checked the boxes for start and end frame, and then subtracted one frame at the end of the file. Then I encoded the file as usual.

In NanDub I combined the DivX .avi with the new .mp3 and lo and behold, the resulting file plays till the end with audio and video!

So, somehow, taking off that last frame did the trick, but I do not know why, nor can I imagine if this will work with the longer videos that I hope to apply this procedure to, for VHS to DivX.

Can anyone shed some light on this, what it might be about my methods above that leads Headac3he to read "less bytes than expected" while encoding audio, and whether this is simply an end frame issue, or if it was just by chance that removing the end frame solved the problem? With many thanks and best wishes.