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• x264 encoded frames into a mp4 container with ffmpeg API

  10 septembre 2019, par PJD

  I'm struggling with understanding what is and what is not needed in getting my already encoded x264 frames into a video container file using ffmpeg's libavformat API.

  



  My current program will get the x264 frames like this -

  



  while( x264_encoder_delayed_frames( h ) )
{
    printf("Writing delayed frame %u\n", delayed_frame_counter++);
    i_frame_size = x264_encoder_encode( h, &nal, &i_nal, NULL, &pic_out );
    if( i_frame_size < 0 ) {
            printf("Failed to encode a delayed x264 frame.\n");
            return ERROR;
        }
    else if( i_frame_size )
    {
        if( !fwrite(nal->p_payload, i_frame_size, 1, video_file_ptr) ) {
            printf("Failed to write a delayed x264 frame.\n");
            return ERROR;
        }
    }
}


  



  If I use the CLI to the ffmpeg binary, I can put these frames into a container using :

  



  ffmpeg -i "raw_frames.h264" -c:v copy -f mp4 "video.mp4"


  



  I would like to code this function into my program using the libavformat API though. I'm a little stuck in the concepts and the order on which each ffmpeg function is needed to be called.

  



  So far I have written :

  



          mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
        printf("Guessed format\n");

        int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
        printf("Created context = %d\n", ret);
        printf("Format = %s\n", mAVFormatContext->oformat->name);

        mAVStream = avformat_new_stream(mAVFormatContext, 0);
        if (!mAVStream) {
            printf("Failed allocating output stream\n");
        } else {
            printf("Allocated stream.\n");
        }

        mAVCodecParameters = mAVStream->codecpar;
        if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            printf("Invalid codec?\n");
        }

        if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
            ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
            if (ret < 0) {
              printf("Could not open output file '%s'", "gen_vid.mp4");
            }
          }

        ret = avformat_write_header(mAVFormatContext, NULL);
        if (ret < 0) {
          printf("Error occurred when opening output file\n");
        }


  



  This will print out :

  



  Guessed format
Created context = 0
Format = mp4
Allocated stream.
Invalid codec?
[mp4 @ 0x55ffcea2a2c0] Could not find tag for codec none in stream #0, codec not currently supported in container
Error occurred when opening output file


  



  How can I make sure the codec type is set correctly for my video ?
Next I need to somehow point my mAVStream to use my x264 frames - advice would be great.

  



  Update 1 :
So I've tried to set the H264 codec, so the codec's meta-data is available. I seem to hit 2 newer issues now.
1) It cannot find the device and therefore cannot configure the encoder.
2) I get the "dimensions not set".

  



  mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
printf("Guessed format\n");

// MUST allocate the media file format context. 
int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
printf("Created context = %d\n", ret);
printf("Format = %s\n", mAVFormatContext->oformat->name);

// Even though we already have encoded the H264 frames using x264,
// we still need the codec's meta-data.
const AVCodec *mAVCodec;
mAVCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!mAVCodec) {
    fprintf(stderr, "Codec '%s' not found\n", "H264");
    exit(1);
}
mAVCodecContext = avcodec_alloc_context3(mAVCodec);
if (!mAVCodecContext) {
    fprintf(stderr, "Could not allocate video codec context\n");
    exit(1);
}
printf("Codec context allocated with defaults.\n");
/* put sample parameters */
mAVCodecContext->bit_rate = 400000;
mAVCodecContext->width = width;
mAVCodecContext->height = height;
mAVCodecContext->time_base = (AVRational){1, 30};
mAVCodecContext->framerate = (AVRational){30, 1};
mAVCodecContext->gop_size = 10;
mAVCodecContext->level = 31;
mAVCodecContext->max_b_frames = 1;
mAVCodecContext->pix_fmt = AV_PIX_FMT_NV12;

av_opt_set(mAVCodecContext->priv_data, "preset", "slow", 0);
printf("Set codec parameters.\n");

// Initialize the AVCodecContext to use the given AVCodec.
avcodec_open2(mAVCodecContext, mAVCodec, NULL);            

// Add a new stream to a media file. Must be called before
// calling avformat_write_header().
mAVStream = avformat_new_stream(mAVFormatContext, mAVCodec);
if (!mAVStream) {
    printf("Failed allocating output stream\n");
} else {
    printf("Allocated stream.\n");
}

// TODO How should codecpar be set?
mAVCodecParameters = mAVStream->codecpar;
if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
    printf("Invalid codec?\n");
}

if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
    ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
    if (ret < 0) {
      printf("Could not open output file '%s'", "gen_vid.mp4");
    }
  }
printf("Called avio_open()\n");

// MUST write a header.
ret = avformat_write_header(mAVFormatContext, NULL);
if (ret < 0) {
  printf("Error occurred when opening output file (writing header).\n");
}


  



  Now I am getting this output -

  



  Guessed format
Created context = 0
Format = mp4
Codec context allocated with defaults.
Set codec parameters.
[h264_v4l2m2m @ 0x556460344b40] Could not find a valid device
[h264_v4l2m2m @ 0x556460344b40] can't configure encoder
Allocated stream.
Invalid codec?
Called avio_open()
[mp4 @ 0x5564603442c0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
[mp4 @ 0x5564603442c0] dimensions not set
Error occurred when opening output file (writing header).


  


• x264 encoded frames into a mp4 container with ffmpeg API

  10 septembre 2019, par PJD

  I'm struggling with understanding what is and what is not needed in getting my already encoded x264 frames into a video container file using ffmpeg's libavformat API.

  



  My current program will get the x264 frames like this -

  



  while( x264_encoder_delayed_frames( h ) )
{
    printf("Writing delayed frame %u\n", delayed_frame_counter++);
    i_frame_size = x264_encoder_encode( h, &nal, &i_nal, NULL, &pic_out );
    if( i_frame_size < 0 ) {
            printf("Failed to encode a delayed x264 frame.\n");
            return ERROR;
        }
    else if( i_frame_size )
    {
        if( !fwrite(nal->p_payload, i_frame_size, 1, video_file_ptr) ) {
            printf("Failed to write a delayed x264 frame.\n");
            return ERROR;
        }
    }
}


  



  If I use the CLI to the ffmpeg binary, I can put these frames into a container using :

  



  ffmpeg -i "raw_frames.h264" -c:v copy -f mp4 "video.mp4"


  



  I would like to code this function into my program using the libavformat API though. I'm a little stuck in the concepts and the order on which each ffmpeg function is needed to be called.

  



  So far I have written :

  



          mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
        printf("Guessed format\n");

        int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
        printf("Created context = %d\n", ret);
        printf("Format = %s\n", mAVFormatContext->oformat->name);

        mAVStream = avformat_new_stream(mAVFormatContext, 0);
        if (!mAVStream) {
            printf("Failed allocating output stream\n");
        } else {
            printf("Allocated stream.\n");
        }

        mAVCodecParameters = mAVStream->codecpar;
        if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
            mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
            printf("Invalid codec?\n");
        }

        if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
            ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
            if (ret < 0) {
              printf("Could not open output file '%s'", "gen_vid.mp4");
            }
          }

        ret = avformat_write_header(mAVFormatContext, NULL);
        if (ret < 0) {
          printf("Error occurred when opening output file\n");
        }


  



  This will print out :

  



  Guessed format
Created context = 0
Format = mp4
Allocated stream.
Invalid codec?
[mp4 @ 0x55ffcea2a2c0] Could not find tag for codec none in stream #0, codec not currently supported in container
Error occurred when opening output file


  



  How can I make sure the codec type is set correctly for my video ?
Next I need to somehow point my mAVStream to use my x264 frames - advice would be great.

  



  Update 1 :
So I've tried to set the H264 codec, so the codec's meta-data is available. I seem to hit 2 newer issues now.
1) It cannot find the device and therefore cannot configure the encoder.
2) I get the "dimensions not set".

  



  mAVOutputFormat = av_guess_format("gen_vid.mp4", NULL, NULL);
printf("Guessed format\n");

// MUST allocate the media file format context. 
int ret = avformat_alloc_output_context2(&mAVFormatContext, NULL, NULL, "gen_vid.mp4");
printf("Created context = %d\n", ret);
printf("Format = %s\n", mAVFormatContext->oformat->name);

// Even though we already have encoded the H264 frames using x264,
// we still need the codec's meta-data.
const AVCodec *mAVCodec;
mAVCodec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!mAVCodec) {
    fprintf(stderr, "Codec '%s' not found\n", "H264");
    exit(1);
}
mAVCodecContext = avcodec_alloc_context3(mAVCodec);
if (!mAVCodecContext) {
    fprintf(stderr, "Could not allocate video codec context\n");
    exit(1);
}
printf("Codec context allocated with defaults.\n");
/* put sample parameters */
mAVCodecContext->bit_rate = 400000;
mAVCodecContext->width = width;
mAVCodecContext->height = height;
mAVCodecContext->time_base = (AVRational){1, 30};
mAVCodecContext->framerate = (AVRational){30, 1};
mAVCodecContext->gop_size = 10;
mAVCodecContext->level = 31;
mAVCodecContext->max_b_frames = 1;
mAVCodecContext->pix_fmt = AV_PIX_FMT_NV12;

av_opt_set(mAVCodecContext->priv_data, "preset", "slow", 0);
printf("Set codec parameters.\n");

// Initialize the AVCodecContext to use the given AVCodec.
avcodec_open2(mAVCodecContext, mAVCodec, NULL);            

// Add a new stream to a media file. Must be called before
// calling avformat_write_header().
mAVStream = avformat_new_stream(mAVFormatContext, mAVCodec);
if (!mAVStream) {
    printf("Failed allocating output stream\n");
} else {
    printf("Allocated stream.\n");
}

// TODO How should codecpar be set?
mAVCodecParameters = mAVStream->codecpar;
if (mAVCodecParameters->codec_type != AVMEDIA_TYPE_AUDIO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_VIDEO &&
    mAVCodecParameters->codec_type != AVMEDIA_TYPE_SUBTITLE) {
    printf("Invalid codec?\n");
}

if (!(mAVFormatContext->oformat->flags & AVFMT_NOFILE)) {
    ret = avio_open(&mAVFormatContext->pb, "gen_vid.mp4", AVIO_FLAG_WRITE);
    if (ret < 0) {
      printf("Could not open output file '%s'", "gen_vid.mp4");
    }
  }
printf("Called avio_open()\n");

// MUST write a header.
ret = avformat_write_header(mAVFormatContext, NULL);
if (ret < 0) {
  printf("Error occurred when opening output file (writing header).\n");
}


  



  Now I am getting this output -

  



  Guessed format
Created context = 0
Format = mp4
Codec context allocated with defaults.
Set codec parameters.
[h264_v4l2m2m @ 0x556460344b40] Could not find a valid device
[h264_v4l2m2m @ 0x556460344b40] can't configure encoder
Allocated stream.
Invalid codec?
Called avio_open()
[mp4 @ 0x5564603442c0] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
[mp4 @ 0x5564603442c0] dimensions not set
Error occurred when opening output file (writing header).


  


• FFmpeg pauses the extraction of frames at 20% (but when closed, dumps all frames to disk)

  1er décembre 2019, par Nicke Manarin

  I’m trying to extract frames from a video using FFmpeg. I want to be able to control which frames to extract, by setting the start, end and FPS values.

  The problem is, that after the extraction begins, FFmpeg stops after 20% of the way. It always stops there, independently of the frame count.

  This is the code that I’m using :

  var start = TimeSpan.FromMilliseconds(SelectionSlider.LowerValue);
  
  var end = TimeSpan.FromMilliseconds(SelectionSlider.UpperValue);
  
  var fps = FpsIntegerUpDown.Value;
  
  var count = CountFrames(); //Duration x FPS
  
  var folder = Path.Combine(RootFolder, "Import");
  
  var path = Path.Combine(folder, $"%0{count.ToString().Length + 1}d.png");
  
  
  
  try
  
  {
  
      //Create temporary folder.
  
      if (Directory.Exists(folder))
  
          Directory.Delete(folder, true);
  
  
  
      Directory.CreateDirectory(folder);
  
  
  
      CaptureProgressBar.Value = 0;
  
      CaptureProgressBar.Maximum = count;
  
  
  
      var info = new ProcessStartInfo(UserSettings.All.FfmpegLocation)
  
      {
  
          Arguments = $" -i \"{VideoPath}\" -vsync 2 -progress pipe:1 -vf scale={VideoWidth}:{VideoHeight} -ss {start:hh\\:mm\\:ss\\.fff} -to {end:hh\\:mm\\:ss\\.fff} -hide_banner -c:v png -r {fps} -vframes {count} \"{path}\"",
  
          CreateNoWindow = true,
  
          ErrorDialog = false,
  
          UseShellExecute = false,
  
          RedirectStandardError = true,
  
          RedirectStandardOutput = true
  
       };
  
  
  
       _process = new Process();
  
       _process.OutputDataReceived += (sender, e) =>
  
       {
  
           Debug.WriteLine(e.Data);
  
  
  
           if (string.IsNullOrEmpty(e.Data))
  
               return;
  
  
  
           var parsed = e.Data.Split('=');
  
  
  
           switch (parsed[0])
  
           {
  
               case "frame":
  
                   Dispatcher?.InvokeAsync(() => { CaptureProgressBar.Value = Convert.ToDouble(parsed[1]); });
  
                   break;
  
  
  
               case "progress":
  
                   if (parsed[1] == "end" && IsLoaded)
  
                       GetFiles(folder); //Get all files from the output folder.
  
  
  
                   break;
  
            }
  
      };
  
  
  
  _process.ErrorDataReceived += (sender, e) =>
  
  {
  
      if (!string.IsNullOrEmpty(e.Data))
  
          throw new Exception("Error while capturing frames with FFmpeg.") { HelpLink = $"Command:\n\r{info.Arguments}\n\rResult:\n\r{e.Data}" };
  
  };
  
  
  
  _process.StartInfo = info;
  
  _process.Start();
  
  _process.BeginOutputReadLine();
  
  
  
  //Just to wait...
  
  await Task.Factory.StartNew(() => _process.WaitForExit());

  So, after starting the import process, FFmpeg will extract some frames, and after reaching around 20%, it will pause the extraction.

  frame=95
  
  fps=5.79
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1400000
  
  out_time_ms=1400000
  
  out_time=00:00:01.400000
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.0854x
  
  
  
  progress=continue
  
  frame=106
  
  fps=6.25
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1583333
  
  out_time_ms=1583333
  
  out_time=00:00:01.583333
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.0933x
  
  progress=continue
  
  
  
  frame=117
  
  fps=6.67
  
  stream_0_0_q=-0.0
  
  bitrate=N/A
  
  total_size=N/A
  
  out_time_us=1766667
  
  out_time_ms=1766667
  
  out_time=00:00:01.766667
  
  dup_frames=0
  
  drop_frames=0
  
  speed=0.101x
  
  progress=continue

  Something strange : if I close the app while is the extraction is paused, suddenly FFmpeg will dump all frames to the folder.

  Why would FFmpeg pause the extraction at all (But continue doing in memory) ?
  Is there any way for me to force FFmpeg to extract the frames normally ?

  PS : It does not happen while using FFmpeg via cmd, so it must be something in code.