2016-03-01, 10:57
(2016-03-01, 08:27)wrxtasy Wrote: Is there any legitimate reason why someone would want to encode HEVC with a Variable Frame Rate in the first place if its causing a bunch of problems ?
It cannot be for any requirement for file sizes as HEVC encoding nice and efficient as it is.
Handbrake stupidly has HEVC encoding set as a Variable Frame Rate by default.
Doesn't it offer encoding efficiencies? Isn't it likely to be used for the same reason that we use dynamic GOP-by-GOP 25p/50i mode-switching on our H264 encoders on DVB-T2 in the UK?
If you have a broadcast stream you are going to be receiving a mix of 'native' frame rates (though the stream to the encoder will be fixed at a single frame rate usually it will have sources of differing rates). In Europe drama will be shot 25p, news, sport and entertainment will be shot 50p (or higher, as 100p is potentially coming). Surely you would want to encode efficiently, so the encoder should detect the 25p-ness of the input source and switch to 25p encoding (halving the number of frames encoded), but when it sees it is being fed 50p (or higher) it would switch to 50p encoding. This may not even be on a show-by-show basis. It could be within a show (50p studio interview with a 25p 'film' clip dropped into it?)
In the US you have an even more complex case of 24p, 29.97p and 59.94p (and probably 119.88p if HFR happens - which is possible) input frame rates - but the final stream could be delivered to the encoder at 59.94/119.88? Lots of efficiencies if you can detect the various source frame rates at the encoder level and avoid coding repeated frames. (Actually I think the Japanese are really pushing for 30.00, 60.00 and 120.00 frame rates - as they tried and failed to do with their original HDTV standard that was tweaked to become 1080/59.94i)
Unless I've got the wrong end of the stick - I think VFR is likely to be pretty important in broadcast implementations of HEVC. Which are likely to be the first 'open' sources of content we have? (I've already got HEVC 2160/59.94p recordings of the 2014 World Cup I made off-air from the BBC DVB-T2 tests here... Am hoping an ODroid C2 will play them :-) )
