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 Post subject: Corrupt video downloads
PostPosted: Mon Apr 05, 2004 5:18 pm 
about 75% of videos I download (mostly tv shows) have audio/video distortion at random places -- the files download just fine without giving any error messages, yet still have this problem

if i re-download the file, sometimes the distortions will go away, but most of the time the video will still have distortion (although the distortion will appear at different points in the video than with the first download)

i ran the memory test suggested on the main page and it said there were no errors

any ideas about this?


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 Post subject:
PostPosted: Mon Apr 05, 2004 7:45 pm 
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Joined: Sun Mar 07, 2004 10:05 am
Posts: 1212
Were you having problems with the downloader reporting corruption? Not just memory problems can cause download corruption, unfortunately; bad memory is the only factor I've been able to identify, and about half the people with corruption problems have them because of it.

As for distortions in the video, it's possible you need a newer or different codec to play it properly. Really, I can only help people send stuff; I can't help them with what they send.


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 Post subject:
PostPosted: Mon Apr 05, 2004 8:06 pm 
sometimes the downloader will report corruption during the download and re-download a piece, sometimes it won't -- but in both cases the end result is often a file that the downloader believes is error-free that isn't

it is not a codec issue -- sometimes when i re-download the same file (same torrent) that had video problems, it plays just fine (and video downloads via other methods, such as emule, work fine) ---

and this is a very specific type of video/audio distortion that i've never seen except with these corrupted torrent downloads -- it involves the picture becoming distorted in several ways (including images on the screen becoming transparent or smearing with the background) -- the audio has several problems as well, including loud pops/beeps and missing audio where the sound that came before and after the audio seems to be compressed together (e.g. if a character is supposed to say "Hello, how are you doing today?" it will sound like "Hell-w are-oing today?" with spurts and pops intermixed in)

is there any info i can give you to help figure this out?


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 Post subject:
PostPosted: Tue Apr 06, 2004 9:11 am 
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Joined: Sun Mar 07, 2004 10:05 am
Posts: 1212
"Redownloading a piece" is normal behavior; it's "download corrupted, please restart" that indicates a serious problem. But the fact that you're getting different data with each download irks me. I suggest you get a CRC-checking tool, such as SecExMD5 (I don't know the page, Google it) to confirm that the download is different. BitTorrent uses a cryptographic hash to verify data, and assuming something isn't broken in the engine, it shouldn't be possible to download something different. The engine looks like it's working fine, too.


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 Post subject:
PostPosted: Wed Apr 07, 2004 11:11 pm 
D:\TV Shows\South Park\south.park.s08e03.xvid-fqm.avi :
MD5: 666AC282A076F23E2B6E5A145FDFC34D
SHA1: 26F0EB9E8828A5B9BDFA6E5692CFE4D700A07664
RIPEMD: F6E3473DE4352305479EE2D626832C753449C81D

D:\TV Shows\South Park\NEW DOWNLAOD\south.park.s08e03.xvid-fqm.avi :
MD5: 1CB80F4FA6085EE37591AAAF4D651682
SHA1: E858626110052B2D3A3BA5F4B2B03B0CEE410783
RIPEMD: 496D31A3FBE33B262BED910B672660F896713472


Downloads are different - confirmed (both are from the same torrrent file - first one has massive video/audio problems; i think the second one is error free but haven't watched the entire thing yet).

I've been seeing this problem across different bittorrent programs too -- I've used various versions of shadow experimental, ABC, and Azureus - got this corruption with all of them.

I just started using your new BitTornado and I selected "Triple-check" error checking -- I've been getting a lot of "download corrupted, please restart" messages with torrents (when I get that message, I've been closing the torrent window, running the torrent file again, and saving it in the same place, so it just continues the old download -- i'm not sure if that's what i'm supposed to do, or if i'm supposed to delete the partial file and start over) ---- I haven't had a chance to watch many of my downloads done with BitTornado + triple-check error -- I'll let you know if I still see this corruption problem with this.


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 Post subject:
PostPosted: Wed Apr 07, 2004 11:46 pm 
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Joined: Mon Mar 15, 2004 8:35 am
Posts: 418
Looking at StorageWrapper.py, "triple check" flushes data to disk, then reads it back and compares the sha1 hash it had before being written to disk with the sha1 hash of it after it is re-read from the disk and only says "download corrupted; please restart and resume" if the information changed when being read back. So it sounds like you have a failing hard drive or a bad IDE connection or even quite possibly a bad IDE chipset driver. Try doing a thorough scandisk of your hard drive, verify your hard drive's IDE cable is firmly connected, and look for any possible IDE chipset updates for your system.


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 Post subject:
PostPosted: Fri Apr 16, 2004 8:30 am 
Scandisk can't find anything wrong with the hard drive (and I've seen the "download corrupted, please restart" message while downloading to two different hard drives).

I think two additional options added to the program would fix all my problems completely -- I bolded those two suggestions in the text below.

I'm getting that "download corrupted, please restart" message fairly frequently (probably an average of 2-3 times per torrent -- with some, I see it 5-10 times before the thing finishes). I'd like to see a user-selectable option for the torrent to automatically continue downloading after getting the "download corrupted, please restart" message (i.e. whenever the program gets data that would have it return that message, instead: (1) have it do that scan it does when you run a torrent and save it on top of a partially downloaded file, and (2) then have it automatically resume downloading from there). It's not very fun to have to manually close a torrent then go run the torrent file again, and tell it to save over the partially downloaded piece (especially when I have to do it 5-10 times for a single torrent).

The good news is that BitTornado with 3x error checking has significantly reduced the number corrupted videos I download -- it hasn't completely eliminated the problem though. Sometimes, the program will indicate a torrent has finished, and it will contain corruption. However, if I then run the torrent again and save on top of the file, the program will say it's only 97% (or something like that) done, and it will continue downloading (so far, doing this has fixed the corruption in all cases). To fix this problem, it'd be great if a user-selectable feature could be added (maybe call it 4x error checking! :P) that would cause the program to run that saving-on-top-of-a-partial-download scan at the end of all torrent downloads before it concludes that it has downloaded 100%.


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 Post subject:
PostPosted: Fri Apr 16, 2004 5:09 pm 
You can also verify your harddrive/chipset driver working correctly if you copy a large file from one harddrive to another and check both files afterwards with a crc-tool or a simple filecompare (fc, windiff). I doubt that this kind of corruption is caused by bittorrent.


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 Post subject:
PostPosted: Sat Apr 17, 2004 2:05 pm 
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Joined: Sun Mar 07, 2004 10:05 am
Posts: 1212
A bad driver/DLL may be the cause of your problem. Unfortunately, there's very little I can do about it. The "auto-restart" option is no good; often it's not simply the download data that's corrupted, but the program in RAM, and that's impossible to recover from reliably.


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