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• Encode Frames to Video with C Library

  31 juillet 2018, par NetherGranite

  For the sake of continuity, let us assume "RGB values" are the following :

  typedef struct RGB {
  
      uint8_t r, g, b;
  
  } rgb;

  However, if you feel that a different color space is more appropriate for this question, please use that instead.

  How might I go about writing 2D arrays of RGB values to a video in C given an output format and framerate ?

  Before I continue, I should specify that I wish to be able to do this all within one program. I am trying to add functionality to an application that would allow it to compile videos frame by frame without having to leave it.

  Additionally, my needs for this functionality are extremely basic ; I simply need to be able to set individual pixels to certain colors.

  The closest I have come to a solution so far is the C library FFmpeg. Allow me to describe what I was able to learn on my own :

  After looking through its documentation, I came across the function avcodec_send_frame(avctx, frame), whose parameters are of the types AVCodexContext* and const AVFrame* respectively. If these are not the right tools for what I am trying to do, please ignore the rest of the question and instead point me towards what I should be using.

  However, I do not know which fields of avctx and frame must be set manually and which do not. The reason I assume some do not is because both are extremely large structures, but correct me if I am wrong.

  Question 1 : What values of an AVCodecContext and AVFrame must be set ? Of these, what is/are the recommended value(s) for each of them ?

  Additionally, I was only able to find instructions on how to initialize an AVFrame (using av_frame_alloc() and av_frame_get_buffer()) but not for an AVCodexConstant.

  Question 2 : Is there a proper way to initialize an AVCodexConstant ? And just in case, is the method of initializing an AVFrame described above correct ? Do any of the fields of either have a proper method of initialization ?

  Also, I was not able to find official documentation on how to take this AVCodexConstant (which I assume contains the video information) and turn it into a video. I apologize if the documentation for this is easy to find and I just missed it.

  Question 3 : How do I turn an AVCodexConstant into a file of a given format ?

  And, given my limited knowledge :

  Question 4 : Are there any other parts to this process that I am missing, and do I have any of the above parts wrong ?

  ---

  Please keep in mind that I found out about FFmpeg for the first time very recently, and as a result, I am a complete beginner to this. Additionally, my experience with C is very limited, so I would greatly appreciate it if you could note which files need to be included with #include.

  Feel free to even go as far as recommending something other than FFmpeg, just as long as it is written in C. I do not need power-user options, but I would greatly prefer flexibility in what audio and video file types the library can handle.

  ---

  Addressing Potential Duplicates

  I appologize for how long this section is ; I just want to have my bases covered. I heavily apologize, however, if this is in fact a duplicate of a question that I was just unable to find.

  • ffmpeg C API documentation/tutorial [closed] — This question was too open-ended and received answers pointing the asker towards a tutorial at dranger.com, a tutorial that confusingly muddied the waters by focusing heavily on a graphics library of choice. Please do not take this as me saying it is bad ; I am just enough of a beginner that I could not wade through it all.
  • Encoding frames to video with ffmpeg — Although this question seems to have been asking the same thing, it is geared towards Unreal Engine 4, and the asker provided sample code, making it difficult for me to understand which of parts of the accepted answer were necessary for me and which were not.
  • How to write frames to a video file ? — While this also asked the same thing, the accepted answer simply provides a command instead of an explanation of code.
  • YUV Raw frames to video stream — While the accepted answer for this question is a command, the question states that it is looking for a way to encode frames generated by C++ code. Is there some way to run commands in code that I haven’t been able to find ?
  • Converting sequenced frames to video — Not only is the asker’s code written in Python, but it also seems to use already-existing image files as frames.
  • How to write bitmaps as frames to H.264 with x264 in C\C++ ? — The accepted answer seems to describe a process that would take multiple applications, but I could be wrong as I am enough of a beginner that I am not sure exactly what it means other than Step 3.
  • How to write bitmaps as frames to Ogg Theora in C\C++ ? — Although it isn’t a problem that the question specifies the ogg format, it is a problem that the accepted answer suggests libtheora, which appears to only work with ogg files.

• FFPROBE get start-time of audio only

  13 février 2023, par Marcus

  I am using this to get the start time of the video and audio :

  


  ffprobe -show_entries stream=start_time -i https://www.website.com/video.mp4


  


  And the response I get is :

  


      ffprobe version 4.3.1 Copyright (c) 2007-2020 the FFmpeg developers
      built with Apple clang version 12.0.0 (clang-1200.0.32.28)
      configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_9 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack
      libavutil      56. 51.100 / 56. 51.100
      libavcodec     58. 91.100 / 58. 91.100
      libavformat    58. 45.100 / 58. 45.100
      libavdevice    58. 10.100 / 58. 10.100
      libavfilter     7. 85.100 /  7. 85.100
      libavresample   4.  0.  0 /  4.  0.  0
      libswscale      5.  7.100 /  5.  7.100
      libswresample   3.  7.100 /  3.  7.100
      libpostproc    55.  7.100 / 55.  7.100
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'https://www.website.com/video.mp4':
      Metadata:
        major_brand     : isom
        minor_version   : 512
        compatible_brands: isomiso2avc1mp41
        encoder         : Lavf58.76.100
      Duration: 00:03:14.85, start: 0.000000, bitrate: 4488 kb/s
        Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 4418 kb/s, 24 fps, 24 tbr, 90k tbn, 48 tbc (default)
        Metadata:
          handler_name    : VideoHandler
        Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 69 kb/s (default)
        Metadata:
          handler_name    : SoundHandler
[STREAM]
start_time=0.000000
[/STREAM]
[STREAM]
start_time=9.892993
[/STREAM]


  


  How can I get only the second stream, which is the audio, and without all the extra info ?

  


  So the response would just be :

  


  


  start_time=9.892993

  


  


• ffmpeg xfade audio out of sync

  1er décembre 2020, par Richard

  hi I am using ffmpeg xfade to concat two clips, the transition looks fine, but the second clip has no audio in the output. I don't find more information about this in https://trac.ffmpeg.org/wiki/Xfade and the official doc. Can I keep the audio of both clips in sync ?

  


  I'm puttting the complete log below, it's massive

  


  ffmpeg -i teacher1.mp4 -i teacher2.mp4 -filter_complex xfade=transition=fadewhite:duration=1:offset=14.5 output.mp4
ffmpeg version 4.3.1-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'teacher1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:00:15.02, start: 0.000000, bitrate: 2447 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 2315 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'teacher2.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:00:15.02, start: 0.000000, bitrate: 1643 kb/s
    Stream #1:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 1509 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #1:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Stream mapping:
  Stream #0:0 (h264) -> xfade:main (graph 0)
  Stream #1:0 (h264) -> xfade:xfade (graph 0)
  xfade (graph 0) -> Stream #0:0 (libx264)
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x64603c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x64603c0] profile High 4:4:4 Predictive, level 4.0, 4:4:4, 8-bit
[libx264 @ 0x64603c0] 264 - core 161 r3018 db0d417 - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 1920x1080, q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
    Metadata:
      encoder         : Lavc58.91.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc58.91.100 aac
frame=  738 fps= 25 q=-1.0 Lsize=    7317kB time=00:00:29.40 bitrate=2038.9kbits/s speed=1.01x    
video:7064kB audio:236kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.241368%
[libx264 @ 0x64603c0] frame I:8     Avg QP:16.56  size:100307
[libx264 @ 0x64603c0] frame P:332   Avg QP:19.50  size: 15211
[libx264 @ 0x64603c0] frame B:398   Avg QP:24.35  size:  3467
[libx264 @ 0x64603c0] consecutive B-frames:  6.2% 62.6%  8.9% 22.2%
[libx264 @ 0x64603c0] mb I  I16..4: 18.7% 60.5% 20.9%
[libx264 @ 0x64603c0] mb P  I16..4:  4.5%  7.6%  0.6%  P16..4: 24.1%  5.6%  1.9%  0.0%  0.0%    skip:55.7%
[libx264 @ 0x64603c0] mb B  I16..4:  0.4%  0.5%  0.1%  B16..8: 14.3%  0.9%  0.1%  direct: 0.4%  skip:83.3%  L0:42.9% L1:53.9% BI: 3.3%
[libx264 @ 0x64603c0] 8x8 transform intra:59.2% inter:84.3%
[libx264 @ 0x64603c0] coded y,u,v intra: 25.3% 11.9% 13.0% inter: 3.2% 1.7% 1.8%
[libx264 @ 0x64603c0] i16 v,h,dc,p: 49% 25% 15% 12%
[libx264 @ 0x64603c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 31% 17% 37%  2%  2%  3%  2%  3%  2%
[libx264 @ 0x64603c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 19% 15%  6%  7%  7%  6%  6%  5%
[libx264 @ 0x64603c0] Weighted P-Frames: Y:3.3% UV:1.5%
[libx264 @ 0x64603c0] ref P L0: 66.0%  8.0% 18.5%  7.5%  0.0%
[libx264 @ 0x64603c0] ref B L0: 84.9% 13.1%  2.0%
[libx264 @ 0x64603c0] ref B L1: 98.8%  1.2%
[libx264 @ 0x64603c0] kb/s:1960.04
[aac @ 0x64d1280] Qavg: 171.394