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I Just Figured Something Out... - RonO's Ramblings

Mar. 28th, 2010 09:37 am I Just Figured Something Out...

Somethings that should have been obvious to me if I'd bothered to think about it.

Because they aren't available in the US through any legitimate means, I downloaded copies of seasons two and three of The Sarah Jane Adventures from a less-than-legitimate source recently. Since these were AVI files, I used a utility to convert them for import into iTunes. Just now I finished watching the first episode, or part one of the first episode, and noticed that the audio kept getting further and further out of sync with the video. I then started watching the second episode and noticed the same thing.

When I mentioned this to Tara, she remembered that the same thing happened on one or both of the similar Dr. Who downloads I'd made (one before the 9th Doctor episodes premiered here in the US, and one when we managed to miss the last episode both of a season and of a multi-part episode due to a move or similar occurrence).

It was then I realized why this happens - the difference between the PAL and NTSC frame rates. I'm betting that during the sequence of pulling these off of British TV in PAL format and converting them to either DVD (for the Dr Who episodes) or iTunes for play on a marginally NTSC environment (NTSC from the DVD, on a US based computer from iTunes) the video is getting converted frame per frame, but the audio remains at the same rate. So over time the audio and the video get further and further out of sync.

Now, if the problem isn't actually present in the Divx encoded .avi files, then there may be a better way to get it converted to play on my NTSC set systems. But if the problem exists in my source material then I'm probably stuck with it. (While writing this up I did find a frame-rate setting in the video convert I used and I'm seeing if it helps - but I'm not remembering which frame rate is which, so I may have just made the problem worse)

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Comments:

From:johnridley
Date:March 28th, 2010 04:55 pm (UTC)
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While I could be snarky and mention that you could just have a player that didn't lock you into one particular file format, I will instead just suggest that you try handbrake.

It's possible that the frame rate is the problem, but that would be severe. After only 25 seconds of play, the audio would be off by 5 seconds.

I don't think there's such a thing as a "us based" computer - the tools should be able to handle the conversion without trouble - in fact it should NOT be converting frame rate at all - if it's 25 FPS, leave it 25 FPS - there are no modern devices that I know of that can't play 25 FPS video just fine, even if you're outputting to an old NTSC 29.97FPS TV set.

A more common source of trouble is variable bitrate audio; many tools can't maintain sync properly, and you have to convert it to fixed bitrate, then mux that in then convert it.

Or you could just look for a file that's already in iTunes format. One of the biggest problems I have when downloading video for the last few years is that !##!@%!! people keep uploading iTunes specific formats instead of more generic AVI, or even better, MKV formats. I often find that the only format available is some iTunes file.
From:nolly
Date:March 29th, 2010 09:02 pm (UTC)
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What's the advantage of converting it over using the free AVI codec available (Flip4Mac, or something like that)? I prefer VLC as a player; it seems less resource intensive leading to smoother playback, but I think I've played AVIs in iTunes, too, though I'd have to be home to check.
From:ladylaetitia
Date:March 31st, 2010 06:45 am (UTC)
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Ummm..... Amazon.com has this (and if you are boycotting Amazon as so many are - it is $34.99 at Best Buy)

The Sarah Jane Adventures: The Complete Second Season ~ Elisabeth Sladen, Daniel Anthony, Tommy Knight, and Yasmin Paige (DVD - Nov. 10, 2009)
Buy new:$32.99

Season 3 is being released in the UK in October

I usually order from the UK - multi-region DVD players are incredibly inexpensive