Recovering 25p frame rate and maintaining audio sync from 720p/60 US broadcast?

[ianken]

Here's the scenario:

I'm trying to convert "Thomas and Friends" as broadcast by PBS in the US in HD. My local affiliate is 720p.

I can recover the original frames without dupes via:

Decimate(cycle=2)
Decimate(cycle=6)

This results is a rate of 24.975 which is what I expect since this stuff was rendered for 25p in the UK.

But in this case I get A/V sync issues when I mux in the original AC3 audio.

I don't mind the wacky framerate. That's fine. How do I get the audio in sync? Do I need to take it down to PCM and let AVISynth muck with it? If so, what's the proper way to do that?

-Ian
:thanks:

[creaothceann]

Try Info to see if the durations of the audio and video streams differ... if that's the case, use AssumeFPS or TimeStretch(rate)?

[ianken]

Some further investigation shows there's definitely something odd going on. On a whim I removed the Decimate() calls and encoded the original frames with the original audio, and the result was the same: audio drifts out of sync the further I got into the program.

Edit: found it. FFMPEG_MPGMUX from dvrmstoolbox was generating MPG files that played fine but somehow confused DGINDEX. Once I used another mux I was able to get AV sync dead on. Ironically the files that work fine as a source for DGIndex do not play smoothly. Fun times.

[MrVideo]

I'm trying to convert "Thomas and Friends" as broadcast by PBS in the US in HD. My local affiliate is 720p.

You do know that PBS actually sends the program to the PBS stations at 1080i? A lot of local PBS stations are downconverting the 1080i to 720p because they have too many subchannels and 1080i looks like crap, so they downconvert.

So, this means that the original 1080i25 is converted to 1080i29.97 and then converted yet again to 720p29.97. To add insult to injury, you are converting yet again. Why?

[2Bdecided]

Depending which series you're looking at, the original master could be almost anything...
http://en.wikipedia.org/wiki/Thomas_and_Friends

I haven't seen many, but some are 50i, some are 25p, most are SD, some are HD. I know film is technically 24p, but whenever it's used in UK TV it's run at 25p.
(I know the wikipedia article seems to say they're all shot on 35mm film, but some certainly aren't - in lots of the early ones, it's a standard 50i video of model trains going around a train track with steam - all quite obviously not 25p!)

The "best" sources of most of the episodes (almost certainly the SD ones) are probably UK DVDs. You can pick complete series up for £3. We're on series 14 in the UK: http://www.five.tv/shows/thomas-and-friends

If you get the UK versions, I guess the video will be fine. Your kids really won't care. ;)
However, if you get the UK versions, they'll have the UK voice-overs, not the American ones you're used to. Your kids probably won't like that! :)

Cheers,
David.