Strange audio bug with some flv movies

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tormod123
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Strange audio bug with some flv movies

Postby tormod123 » Tue Jan 18, 2011 5:46 pm

First off, forgive me if this has been asked before. I did as many exhaustive a searches as I could think of, but failed to find anything relevant.

I'm having a weird problem with some, and only some, .flv files. I'll use one as an example.

The audio stopped playing after two minutes, then started back up at four minutes but with the audio lagging by those two minutes. (does that make sense?)
It was the same in QT10, QT7 Pro & Nice Player
The file was downloaded from the net using Firefox download helper.
I checked the video length on its site and it was 10' 20" but the flv file showed 12' 21'

I saved the file as a .mov (just saved, not exported to anything else) and dragged it into garageband. This showed two minutes of silence at the end of the video. Trimmed the audio, exported the vid, and all is good so it's nothing major. I'm more curious than anything else.

I'm using Perian 1.2.1 on an Intel MBP running 10.6.6

Any thoughts?

gbooker
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Re: Strange audio bug with some flv movies

Postby gbooker » Tue Jan 18, 2011 6:27 pm

Can you provide the file so we can examine it?

tormod123
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Re: Strange audio bug with some flv movies

Postby tormod123 » Tue Jan 18, 2011 6:37 pm

Thanks for the quick response. Much appreciated.

I'll try to remember the exact file (they're all video tutorials, so there are lots!).
Is Dropbox a suitable place to upload it? If not, let me know what is.

[Edit] Actually, the file I used as an example wasn't an internet one. It was part of an application install DVD, so I can zip the html, swf, images etc. as well as the flv.

[Edit 2] I'm sure you'll tell me if this is not a good upload place:

http://dl.dropbox.com/u/12177874/Tormod ... _Audio.zip

gbooker
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Re: Strange audio bug with some flv movies

Postby gbooker » Wed Jan 19, 2011 1:10 am

Dropbox is perfectly fine.

I'm getting a different result here. In scrubbing, I didn't find any audio gaps. I did notice that the video is 10:20 and the audio is 9:53. If I recompose the tracks so they length is the same, the audio sync is never lost.

I'm running Perian for SVN, so some of the issues may be fixed. I'll look at the file some more when I have time to see if I can figure out the track durations.

gbooker
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Re: Strange audio bug with some flv movies

Postby gbooker » Thu Jan 20, 2011 2:16 am

Since I found the technical details and the details are typically better expressed on trac, I opened a new ticket there: http://trac.perian.org/ticket/543

tormod123
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Re: Strange audio bug with some flv movies

Postby tormod123 » Thu Jan 20, 2011 3:53 pm

I'm pleased it's fixable.
Not sure I'm brave enough to delve into the source code and try to patch and rebuild myself – I think I'll wait for the next release :smile:

Thanks for updating the thread as well.


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