Re: [FFmpeg-user] Increasing the decoding speed of yuv444p h.264 files
On 5/18/2015 7:22 PM, Yan Li wrote: I've done some more tests. Input file src.flv is in yuv444p with 48 fps. I use the following commands to generate two lossless test files: 1: ffmpeg -i src.flv -c:v libx264 -qp 0 -preset ultrafast -an yuv444p.mkv 2: ffmpeg -i src.flv -c:v libx264 -qp 0 -preset ultrafast -pix_fmt yuv420p -an yuv420p.mkv Then I test the decoding speed using: time ffmpeg -i yuv444p.mkv -f rawvideo -an - /dev/null - yuv444p.mkv (496 Mb/s): decoded at 55 fps - yuv420p.mkv (336 Mb/s): decoded at 92 fps (I/O is not the bottleneck here. Four threads are used.) sorry to question, but: are you really sure about this? those are really high bitrates and it appears to be a direct link between bitrate and decoding speed: 496 x 55 ~= 336 x 92 (by a 10% margin). I don't know what's the drive access pattern in this case but if seeks just a bit, you have a problem. as a test, I would encode at much smaller bitrates and then compare the fps. of course, you can measure the disk I/O load with appropriate tools during decoding. -- Claudiu ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
Re: [FFmpeg-user] Increasing the decoding speed of yuv444p h.264 files
On Mon, May 18, 2015 at 2:00 AM, Carl Eugen Hoyos ceho...@ag.or.at wrote: Yan Li elliot.li.tech at gmail.com writes: 2. I want to archive the files in yuv444p. Is there any option that can make ffplay play these files faster? I don't mind losing replay quality for now, but I do need to keep yuv444p files. Please test and report, I would expect that different encoding options imply different decoding speeds. I've done some more tests. Input file src.flv is in yuv444p with 48 fps. I use the following commands to generate two lossless test files: 1: ffmpeg -i src.flv -c:v libx264 -qp 0 -preset ultrafast -an yuv444p.mkv 2: ffmpeg -i src.flv -c:v libx264 -qp 0 -preset ultrafast -pix_fmt yuv420p -an yuv420p.mkv Then I test the decoding speed using: time ffmpeg -i yuv444p.mkv -f rawvideo -an - /dev/null - yuv444p.mkv (496 Mb/s): decoded at 55 fps - yuv420p.mkv (336 Mb/s): decoded at 92 fps (I/O is not the bottleneck here. Four threads are used.) A player that outputs video are slower than pure ffmpeg decoding, thus the 48 fps yuv444p.mkv looks choppy on my machine. Iirc, there is a x264 option that makes the output file decode faster. I'm aware of that option. I can't find this documented anywhere, but it seems to me that fastdecode has no effect on lossless encoding. I do have lossy files too. But they are for archive purpose, and I don't want to sacrifice quality/compression ratio for decoding speed; I bet future hardware would have no problem playing them. 3. Are there any chance that the software (ffmpeg or x264/x265) can get better optimized in the near future (1 or 2 years?) I don't have a crystal ball but I can say that this was the case in the past (but this is also something you could test). I guess the color space conversion itself can't explain the huge gap in decoding speed. So it is actually ffmpeg's yuv444p decoding is compute-intensive. I think what I want to know is whether the code is already fully optimized/SIMDized, because h264 has been standardized for a decade, and I'm not sure if someone is still actively optimizing ffmpeg's h264 decoder. If that's the case I won't expect magic to happen in the near future, and will just wait for my budget to buy new hardware. But heck, what do I know about ffmpeg, I won't be surprised if I were totally wrong. -- Yan ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
Re: [FFmpeg-user] Increasing the decoding speed of yuv444p h.264 files
On Mon, May 18, 2015 at 09:00:36 +, Carl Eugen Hoyos wrote: Iirc, there is a x264 option that makes the output file decode faster. Indeed: --tune fastdecode, which maps to ffmpeg's libx264's -tune fastdecode (Note that using -preset will change some of those settings additionally. I don't know which of the two options wins or how they mix.) See also http://superuser.com/questions/564402/explanation-of-x264-tune Moritz ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
Re: [FFmpeg-user] Increasing the decoding speed of yuv444p h.264 files
Yan Li elliot.li.tech at gmail.com writes: 2. I want to archive the files in yuv444p. Is there any option that can make ffplay play these files faster? I don't mind losing replay quality for now, but I do need to keep yuv444p files. Please test and report, I would expect that different encoding options imply different decoding speeds. Iirc, there is a x264 option that makes the output file decode faster. 3. Are there any chance that the software (ffmpeg or x264/x265) can get better optimized in the near future (1 or 2 years?) I don't have a crystal ball but I can say that this was the case in the past (but this is also something you could test). Carl Eugen ___ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
