Decomb Bob and Detelecine

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randomreuben
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Decomb Bob and Detelecine

Post by randomreuben »

Dear devs,

If in the past I had issues with detelecine and anime, I simply used decomb. I have tried the new decomb bob and it produces the most beautiful results. So I was wondering, is there anything wrong with using decomb bob for everything? Will I have any stuttering issues if I simply use decomb bob and not detelecine again. I don't mind the larger file sizes at all. I have terabytes to spare. Do you know if decomb bob and telecined materials will play well together? So far I have tried out a couple of DVDs and it's mostly fine but there is a stutter or two once in a while. I don't know if that's the player or the encoded file. Any thoughts? A log file for a telecined DVD is here. viewtopic.php?f=6&t=24177&start=25#p111840

Thanks!

mduell
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Re: Decomb Bob and Detelecine

Post by mduell »

For simple/cleanly telecined sources, detelecine is best.

Bob doubles the framerate, so the output at 50 or 60fps isn't compatible with many playback devices that only support 30fps (Apple iDevices, etc).

randomreuben
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Re: Decomb Bob and Detelecine

Post by randomreuben »

That's true, but I really like the decomb output and I just want the simplicity of leaving one preset on for everything. If decomb bob is known to play nice with weird instances of telecined material, then I'll use decomb bob for everything and just simplify my life. But that's what I'm hoping someone here knows, whether you can use decomb bob without the chance of any trouble with telecined sources.

mduell
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Re: Decomb Bob and Detelecine

Post by mduell »

It's not ideal (bloats file size at a given quality), but I don't think you'll have any problems with bobbing telecined sources.

randomreuben
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Re: Decomb Bob and Detelecine

Post by randomreuben »

Exactly the answer I was hoping to get. Spectacular!

moneymatt4life
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Re: Decomb Bob and Detelecine

Post by moneymatt4life »

whenever i deal with telecined material (meaning dvd material... but sometimes sometimes tv sources follow telecine pattern... in which it's fine to use detelecine...) but most telecined material don't follow the full 3:2 pattern... it usually changes throughout the video... so i ALWAYS use detelecine AND default decomb... as this usually ALWAYS takes care of those extra telecined frames that detelecine doesn't fix. (although i've been told that detelecine can detect telecine frame changes... but it doesn't sadly... otherwise you wouldn't need both detelecine and decomb) so you should always have detelecine and default decomb when dealing with telecined material (meaning that you have personally checked that the source is telecined meaning 3 regular frames and 2 interlaced frames) BUT you should always check to see if the source is INDEED telecined as some dvd sources aren't... (some dvd sources are interlaced for 4 or full 5 frames... in which default or bob decomb would be best to use...)
mduell wrote:... so the output at 50 or 60fps isn't compatible with many playback devices that only support 30fps (Apple iDevices, etc).
i don't know about all the other iDevices but i know for sure that iPod touch 4th gen supports at least 59.94fps... i never tried 60fps... as doubling dvd source framerate is 59.94fps... but even then i don't typically use it when using detelecine and decomb... i only use 59.94 when i'm bobbing interlaced tvsources (480i mpgs and 1080i ts/mpgs) and it plays perfectly fine on iPod 4th gen...

IrishPrince
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Re: Decomb Bob and Detelecine

Post by IrishPrince »

I have a copy of Super Bowl 46 that has a frame rate of 59.94 FPS and it plays back perfectly on AppleTV 3 and ATV2. Looks stunning in 720p (~ 5190 Kbps video bit rate).
-IP

musicvid
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Re: Decomb Bob and Detelecine

Post by musicvid »

Many interlaced sources report as 29.97i or 59.94i -- they are interchangeable.
Progressive source is reported as 29.97p or 59.94p -- they are actually different frame rates.

rachel
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Re: Decomb Bob and Detelecine

Post by rachel »

I think I'm finding that on some sources (off-air BBC HD transport streams mostly) I think the decomb filter may be finding false positives, ie: doing decombing where there's no combing or interlacing artifacts that I can see in the original. With decomb-bob this seems to be resulting in sequences where the playback framerate (as observed in plex) fluctuates from the normal 25fps up to around 30-35fps. That's an average over time (probably a second) so I'm guessing reflects the bob-decombing of just a few frames in those seconds. That can happen in shots where, if it was truly interlaced, you'd expect it to be solidly so, like a smooth medium-speed pan right or left. It generally *looks* OK to the eye, so I'm not sure what I'm seeing. Sometimes I think I see timing glitches but not sure how much it's because I'm suspicious and looking for them now.

Where the source most definitely is interlaced at least in parts - eg: the end-titles of almost every TV show, but also other definitely-interlaced sequences - the framerate pops straight up to a solid 50fps, which is what I'd expect.

So I'm starting to be a bit wary of using bob-decomb indiscriminately. Especially where I think the original programme is effectively progressive (yes, transmitted 1080i but the source is progressive) until the end credit roll. Not sure that making *that* beautifully smooth is worth possibly storing up playback troubles on unknown future players I may want to use for the rest of the programme.

Re-encoding some recent stuff I'd encoded with bob-decomb to see what I see with no-deinterlace at all. Making this as an observation on this thread but not ready to write a new bug-report post yet.

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