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• what is the lowest allowed framerate of VP9 codec

  5 janvier 2020, par d3im

  I was searching over Net to find what is the lowest allowed framerate of VP9 but didn't find anything. I'm asking because I successfully encoded video at 0.25 or 1 FPS to x264 or x265, but with VP9 it gives me an error on that framerates.

• Remove extra SPS and PPS from h264 stream

  3 janvier 2020, par izambl

  I have some screen recordings taken with Chrome MediaStream, but Mac Chrome 79 introduced a bug (https://bugs.chromium.org/p/chromium/issues/detail?id=1034633) that breaks some of the videos because of the way SPS and PPS are handled.

  I found out that if I reencode the video with ffmpeg -i video.mp4 -c:v libx264 video1.mp4 it works but it takes too long to process, so I was thinking on converting the stream to AVCC or maybe another way of removing any extra SPS and PPS data so chrome won't use SPS and PPS from IDR slice headers.

  I tried using FFmpeg Bitstream Filters but I couldn't get a working video.

  Is it possible to do without reencoding the full video?

• ffmpeg x264 CPU core scaling

  15 décembre 2019, par alex416

  Does anyone have any experence with this type of thing? Currently using a Ryzen 7 8c/16T CPU, and using a program called BES. Using 10% CPU, is almost no slower at transcoding from mkv to mp4 (both x264, i know i can just copy them) than using 100% cpu on all 16 threads. So, Since this is the case, What is the ideal core count for libx264? I mean, Does the same type of thing happen with 32 threads? Or 8 threads, etc.

• Force x264 to encode all frames relative to the first (IDR) frame

  12 décembre 2019, par cloudraven

  I want to generate a h.264 stream in which P-frames are using references exclusively using a long-term reference to the first frame (an IDR frame). This would also require the first frame to be an IDR frame.

  This is an academic experiment to understand the encoding behavior of long-term references and the consequences of forcing frames to refer to a specific (single) frame rather than several.

  It would be great if I could do this from the command line, but if not possible I am open to modifying x264 for this purpose.

  Could anyone point me to where in the source code it is determined:

  • the reference frame / macroblock / partition for the current macroblock
  • changes made to the short term, long term reference frame list
  • whether to use a short term reference frame or a long term reference frame.

  Using another encoder like nvenc is also acceptable.

• Force x264 to only use long term reference frames

  12 décembre 2019, par cloudraven

  I want to generate a h.264 stream in which P-frames are using references exclusively using long-term references identifiers rather than defaulting to a short-term reference given by the previous frame.

  At this point this is an academic experiment to understand the encoding behavior of long-term references and the consequences of forcing frames to refer to a specific frame rather than several.

  It would be great if I could do this from the command line, but if not possible I am open to modifying x264 for this purpose.

  Could anyone point me to where in the source code it is determined:

  • the reference frame / macroblock / partition for the current macroblock
  • changes made to the short term, long term reference frame list
  • whether to use a short term reference frame or a long term reference frame.

  Using another encoder like nvenc is also acceptable.