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• Is there a way to generate ffmpeg command-lines by analyzing an existing video file ?

  24 décembre 2014, par PreservedMoose

  Is there a tool or technique that is able to generate a valid ffmpeg encode command, based on the properties of an existing source file ?

  In other words, I’d like to take an H264 QuickTime file, run it through the aforementioned (possibly) mythical tool, and have it spit out an ffmpeg command line that can be used to encode another video that matches the exact specs of the source file.

  Apple’s Compressor has similar functionality, where you can just drag a Quicktime file to the Compressor Presets window, and it will automatically create an encoding preset that matches the specs of that file.

  Is there a similar way to achieve this with ffmpeg ?

• ffmpeg determine correct codec to use

  6 janvier 2015, par nha

  I am trying to use .y4m files that I feed into Chrome for playing.
  This is the only format that I can use.

  I have a set of .y4m files that are working for my use case, taken from here.
  For example let’s say that I use the file mobile_qcif_7.5fps.y4m.

  I also have a .mp4 file (specifically the sample small.mp4 file from techslides ). I know how to convert small.mp4 to small.y4m with the following command :

  ffmpeg -y -i small.mp4 small.y4m

  I would like the resulting file to be accepted by Chrome, just like the other file.
  What options should I use (and how to find them) ?

  Additional information

  ffprobe gives :

  $ ffprobe small.y4m 
  
  avprobe version 0.8.13-6:0.8.13-0ubuntu0.13.10.1, Copyright (c) 2007-2014 the Libav developers
  
    built on Jul 15 2014 13:48:35 with gcc 4.8.1
  
  [yuv4mpegpipe @ 0x23160c0] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, yuv4mpegpipe, from 'small.y4m':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0.0: Video: rawvideo, yuv420p, 560x320, 30 fps, 30 tbr, 30 tbn, 30 tbc
  
  
  
  
  
  $ ffprobe mobile_qcif_7.5fps.y4m
  
  avprobe version 0.8.13-6:0.8.13-0ubuntu0.13.10.1, Copyright (c) 2007-2014 the Libav developers
  
    built on Jul 15 2014 13:48:35 with gcc 4.8.1
  
  [yuv4mpegpipe @ 0x1e080c0] max_analyze_duration reached
  
  [yuv4mpegpipe @ 0x1e080c0] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, yuv4mpegpipe, from 'mobile_qcif_7.5fps.y4m':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0.0: Video: rawvideo, yuv420p, 176x144, PAR 128:117 DAR 1408:1053, 7.50 fps, 7.50 tbr, 7.50 tbn, 7.50 tbc

  OS : I am using ffmpeg in Ubuntu 13.10 from the default repository : I ran sudo apt-get install ffmpeg libavcodec-extra-53

  Complete console output

  $ ffmpeg -y -i small.mp4 small.y4m
  
  ffmpeg version 0.8.13-6:0.8.13-0ubuntu0.13.10.1, Copyright (c) 2000-2014 the Libav developers
  
    built on Jul 15 2014 13:48:35 with gcc 4.8.1
  
  *** THIS PROGRAM IS DEPRECATED ***
  
  This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'small.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42isomavc1
  
      creation_time   : 2010-03-20 21:29:11
  
      encoder         : HandBrake 0.9.4 2009112300
  
    Duration: 00:00:05.56, start: 0.000000, bitrate: 551 kb/s
  
      Stream #0.0(und): Video: h264 (Constrained Baseline), yuv420p, 560x320, 465 kb/s, 30 fps, 30 tbr, 90k tbn, 60 tbc
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
      Stream #0.1(eng): Audio: aac, 48000 Hz, mono, s16, 83 kb/s
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
  [buffer @ 0x7274e0] w:560 h:320 pixfmt:yuv420p
  
  Output #0, yuv4mpegpipe, to 'small.y4m':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42isomavc1
  
      creation_time   : 2010-03-20 21:29:11
  
      encoder         : Lavf53.21.1
  
      Stream #0.0(und): Video: rawvideo, yuv420p, 560x320, q=2-31, 200 kb/s, 90k tbn, 30 tbc
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press ctrl-c to stop encoding
  
  frame=  166 fps=  0 q=0.0 Lsize=   43576kB time=5.53 bitrate=64513.5kbits/s    
  
  video:0kB audio:0kB global headers:0kB muxing overhead inf%

  Head of the files

  Not sure if this is relevant, but the text content of both files begin like that :

  mobile_qcif_7.5fps.y4m
  
  YUV4MPEG2 W176 H144 F15:2 Ip A128:117
  
  FRAME
  
  
  
  small.y4m (invalid)
  
  YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420mpeg2 XYSCSS=420MPEG2
  
  FRAME

  Additional experiment

  Taking the sample mobile_qcif_7.5fps.y4m, turning it into a .mp4 file and then back into a .y4m produces an invalid file (at least for Chrome).

  Answer to comments in the answer of @SirDarius

  Following the suggestion of @SirDarius ; I tried the following commands.
  They failed to produce a valid file.

  # [COMMAND]   # [RESULT] [HEADER]
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -pix_fmt yuv444p -y small_yuv444p.y4m   # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C444 XYSCSS=444
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -pix_fmt yuv422p -y small_yuv422p.y4m   # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C422 XYSCSS=422
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -pix_fmt yuv420p -y small_yuv420p.y4m   # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420mpeg2 XYSCSS=420MPEG2
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -pix_fmt yuv411p -y small_yuv411p.y4m   # KO   YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C411 XYSCSS=411
  
  
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -strict -1 -pix_fmt yuv420p9 -y small_yuv420p9.y4m   # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420p9 XYSCSS=420P9
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -strict -1 -pix_fmt yuv420p12 -y small_yuv420p12.y4m # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420p12 XYSCSS=420P12
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -strict -1 -pix_fmt yuv420p14 -y small_yuv420p14.y4m # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420p14 XYSCSS=420P14
  
  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -strict -1 -pix_fmt yuv420p16 -y small_yuv420p16.y4m # KO YUV4MPEG2 W560 H320 F15:2 Ip A0:0 C420p16 XYSCSS=420P16

  When trying other formats (like yuv420p12be, which was in the output of -pix_fmts), I had the following output (hence my previous trials) :

  $  ffmpeg -i small.mp4 -vf fps=7.5 -an -c:v rawvideo -f yuv4mpegpipe -pix_fmt yuv420p12be -y small_yuv420p12be.y4m 
  
  ffmpeg version N-68884-g3ebd76a Copyright (c) 2000-2015 the FFmpeg developers
  
    built on Jan  6 2015 11:03:21 with gcc 4.8 (Ubuntu/Linaro 4.8.1-10ubuntu9)
  
    configuration: 
  
    libavutil      54. 16.100 / 54. 16.100
  
    libavcodec     56. 19.100 / 56. 19.100
  
    libavformat    56. 18.100 / 56. 18.100
  
    libavdevice    56.  3.100 / 56.  3.100
  
    libavfilter     5.  6.100 /  5.  6.100
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x21d0220] overread end of atom 'colr' by 1 bytes
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'small.mp4':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42isomavc1
  
      creation_time   : 2010-03-20 21:29:11
  
      encoder         : HandBrake 0.9.4 2009112300
  
    Duration: 00:00:05.57, start: 0.000000, bitrate: 551 kb/s
  
      Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709), 560x320, 465 kb/s, 30 fps, 30 tbr, 90k tbn, 60 tbc (default)
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
        encoder         : JVT/AVC Coding
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 83 kb/s (default)
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
  [yuv4mpegpipe @ 0x21d8180] ERROR: yuv4mpeg can only handle yuv444p, yuv422p, yuv420p, yuv411p and gray8 pixel formats. And using 'strict -1' also yuv444p9, yuv422p9, yuv420p9, yuv444p10, yuv422p10, yuv420p10, yuv444p12, yuv422p12, yuv420p12, yuv444p14, yuv422p14, yuv420p14, yuv444p16, yuv422p16, yuv420p16 and gray16 pixel formats. Use -pix_fmt to select one.
  
  Output #0, yuv4mpegpipe, to 'small_yuv420p12be.y4m':
  
    Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42isomavc1
  
      encoder         : Lavf56.18.100
  
      Stream #0:0(und): Video: rawvideo ([12][11]3Y / 0x59330B0C), yuv420p12be, 560x320, q=2-31, 200 kb/s, 7.50 fps, 7.50 tbn, 7.50 tbc (default)
  
      Metadata:
  
        creation_time   : 2010-03-20 21:29:11
  
        encoder         : Lavc56.19.100 rawvideo
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (h264 (native) -> rawvideo (native))
  
  Could not write header for output file #0 (incorrect codec parameters ?): Input/output error

  After that, I also tried to edit with an hexadecimal editor (bless) the small_yuv420p.y4m file. I replace C420mpeg2 by C420, and the file was accepted by Chrome.
  What does the number in 420p[number] correspond to ? It is not explained there.
  Is there any way to make ffmpeg output this kind of header files ?

  @SirDarius, thank you again for your help.

  The question

  (in case you forgot after this text blob)

  How can I convert the small.mp4 into a small.y4m file that has the same properties as the mobile_qcif_7.5fps.y4m file ?

• ffmpeg : convert a video by using another video's settings

  11 janvier 2015, par orcaman

  I have an mp4 file containing an H.264 video. This video has particular settings that I am not sure about, but I want to reproduce them on other videos that I encode (those other videos are already H.264 encoded, but they have different properties - bitrate, size, etc.)

  I know that ffprobe can be used to extract some information from the original video, and I guess that using this information I could try to reproduce the conversion settings required for use with other videos.

  Question is : do I have to do this manually, in the sense that I need to map the output of ffprobe to ffmpeg flags ? Is there a better way to do this, to make sure I don’t miss anything ?