Recherche avancée

Sur d’autres sites (9294)

• Best logical formula to determine perceptual / "experienced" quality of a video, given resolution / fps and bitrate ?

  20 mars 2023, par JamesK

  I am looking for a formula that can provide me with a relatively decent approximation of a Video's playback quality that can be calculated based off of four metrics : width, height, fps, and bitrate (bits/sec). Alternatively, I can also use FFMPEG or similar tools to calculate a Video's playback quality, if any of those tools provide something like what I am looking for here.

  


  An example of what a Video might look like in my problem is as follows :

  


  interface Video {
  /** The width of the Video (in pixels). */
  width: number
  /** The height of the Video (in pixels). */
  height: number
  /** The frame rate of the Video (frames per second). */
  fps: number
  /** The bitrate of the video, in bits per second (e.g. 5_000_000 = 5Mbit/sec) */
  bitrate: number
}


  


  I came up with the following function to compute the average amount of bits available for any given pixel per second :

  


  const computeVideoQualityScalar = (video: Video): number => {
  // The amount of pixels pushed to the display, per frame.
  const pixelsPerFrame = video.width * video.height
  
  // The amount of pixels pushed to the display, per second.
  const pixelsPerSecond = pixelsPerFrame * video.fps
  
  // The average amount of bits used by each pixel, each second,
  // to convey all data relevant to that pixel (e.g. color data, etc)
  const bitsPerPixelPerSecond = video.bitrate / pixelsPerSecond
  
  return bitsPerPixelPerSecond
}


  


  While my formula does do a good job of providing a more-or-less "standardized" assessment of mathematical quality for any given video, it falls short when I try to use it to compare videos of different resolutions to one another. For example, a 1080p60fps video with a bitrate of 10Mbit/sec has a greater visual fidelity (at least, subjectively speaking, to my eyes) than a 720p30fps video with a bitrate of 9Mbit/sec, but my formula would score the 720p30fps video significantly higher than the 1080p60fps video because the 720p video has more bits available per pixel per second than the 1080p video.

  


  I am struggling to come up with ideas as to how to either come up with a different way to calculate the "subjective video quality" for a given video, or extend upon my existing idea here.

  


• FFmpeg stdin "output file is empty, nothing was encoded"

  2 février 2023, par brock

  Just trying to stdin and stdout a simple CAF to MP3 conversion. Output looks exactly the same except using stdin does not encode anything. Windows 10. I'm going bananas here. Please advise.

  


  Using - (stdin)...

  


  >type test.caf | ffmpeg -i - -f mp3 - > test.mp3
ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190807
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, caf, from 'pipe:':
  Metadata:
    approximate duration in seconds: 3.1
    source bit depth: I16
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Audio: adpcm_ima_qt (ima4 / 0x34616D69), 48000 Hz, stereo, s16p, 384 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (adpcm_ima_qt (native) -> mp3 (libmp3lame))
Output #0, mp3, to 'pipe:':
  Metadata:
    approximate duration in seconds: 3.1
    source bit depth: I16
    TSSE            : Lavf58.29.100
    Stream #0:0: Audio: mp3 (libmp3lame), 48000 Hz, stereo, s16p
    Metadata:
      encoder         : Lavc58.54.100 libmp3lame
size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)


  


  Using -i...

  


  >ffmpeg -i test.caf -f mp3 - > test.mp3
ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190807
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, caf, from 'test.caf':
  Metadata:
    approximate duration in seconds: 3.1
    source bit depth: I16
  Duration: N/A, start: 0.000000, bitrate: N/A
    Stream #0:0: Audio: adpcm_ima_qt (ima4 / 0x34616D69), 48000 Hz, stereo, s16p, 384 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (adpcm_ima_qt (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'pipe:':
  Metadata:
    approximate duration in seconds: 3.1
    source bit depth: I16
    TSSE            : Lavf58.29.100
    Stream #0:0: Audio: mp3 (libmp3lame), 48000 Hz, stereo, s16p
    Metadata:
      encoder         : Lavc58.54.100 libmp3lame
size=      49kB time=00:00:03.12 bitrate= 129.3kbits/s speed=34.4x
video:0kB audio:49kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.246501%


  


  EDIT : Command syntax is ok. Works as expected with a WAV file. I upgraded FFmpeg now I get errors using stdin. So it is the file that is to blame. However, I do find it odd that using -i is fine, but stdin is not.

  


  >ffmpeg -i - -f mp3 - > test.mp3 < test.caf
ffmpeg version 5.1.2-full_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 12.1.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
[caf @ 0000023dc65b1140] skipping CAF chunk: 00000000 ([0][0][0][0]), size 0
    Last message repeated 324 times
[caf @ 0000023dc65b1140] skipping CAF chunk: 00000000 ([0][0][0][0]), size 431131746560
[caf @ 0000023dc65b1140] skipping CAF chunk: 00000000 ([0][0][0][0]), size 173911953188585728
[caf @ 0000023dc65b1140] skipping CAF chunk: 00FFFF02 ([0][255][255][2]), size -7250317618881344622
pipe:: Invalid data found when processing input


  


• Embedding "Dolby Digital Plus with Dolby Atmos" into MP4 using ffmpeg

  8 mars, par Krystian

  How can I encode Dolby Atmos into MP4 ? I am using this command ffmpeg -i input.mp4 -i input.ec3 -map 0:v -map 1:a -c:v copy -c:a copy -disposition:a default -metadata:s:a:0 complexity_index=16 -metadata:s:a:0 title="Dolby Atmos" output_test.mp4 I have to provide every single piece of data that is inside this EC3 file. I have noticed that when I am running this command the MP4 file contains actual Dolby Atmos stream but it's missing complexity index. Raw EC3 file has Complexity Index set to 16 but after adding it to MP4 file the complexity index is not present and this MP4 is not identified as a video with proper Dolby Atmos stream

  


  I thought that after using this command, complexity index will be added correctly. I don't want to use MKV but it looks like I will have to do that.