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• Delphi, TBitmap (rgb) to YCbCr colors format

  18 octobre 2019, par Alexander M.

  have a video encoding example from http://www.delphiffmpeg.com - need to convert a set of TBitmaps to YCbCr (YUV), how should we do it ? the example contains dummy colors :

    (* encode 1 second of video *)
  
    idx := 1;
  
    for i := 0 to 25 - 1 do
  
    begin
  
      av_init_packet(@pkt);
  
      pkt.data := nil;    // packet data will be allocated by the encoder
  
      pkt.size := 0;
  
  
  
      //fflush(stdout);
  
      (* prepare a dummy image *)
  
      (* Y *)
  
      for y := 0 to c.height - 1 do
  
        for x := 0 to c.width - 1 do
  
          PByte(@PAnsiChar(frame.data[0])[y * frame.linesize[0] + x])^ := x + y + i * 3;
  
  
  
      (* Cb and Cr *)
  
      for y := 0 to c.height div 2 - 1 do
  
        for x := 0 to c.width div 2 - 1 do
  
        begin
  
          PByte(@PAnsiChar(frame.data[1])[y * frame.linesize[1] + x])^ := 128 + y + i * 2;
  
          PByte(@PAnsiChar(frame.data[2])[y * frame.linesize[2] + x])^ := 64 + x + i * 5;
  
        end;
  
  
  
      frame.pts := i;
  
  
  
      (* encode the image *)
  
      ret := avcodec_encode_video2(c, @pkt, frame, @got_output);
  
      if ret < 0 then
  
      begin
  
        Writeln(ErrOutput, 'Error encoding frame');
  
        ExitCode := 1;
  
        Exit;
  
      end;
  
  
  
      if got_output <> 0 then
  
      begin
  
        Writeln(Format('Write frame %d (size=%d)', [idx, pkt.size]));
  
        FileWrite(f, pkt.data^, pkt.size);
  
        av_packet_unref(@pkt);
  
        Inc(idx);
  
      end;
  
    end;

  But we need to convert bitmaps to YCbCr..instead of filling pixels with dummy image. Here is a full source code :

  (*
  
   * Video encoding example
  
   *)
  
  procedure video_encode_example(const filename: string; codec_id: TAVCodecID);
  
  const
  
    endcode: array[0..3] of Byte = ( 0, 0, 1, $b7 );
  
  var
  
    codec: PAVCodec;
  
    c: PAVCodecContext;
  
    idx, i, ret, x, y, got_output: Integer;
  
    f: THandle;
  
    frame: PAVFrame;
  
    pkt: TAVPacket;
  
  begin
  
    Writeln(Format('Encode video file %s', [filename]));
  
  
  
    (* find the mpeg1 video encoder *)
  
    codec := avcodec_find_encoder(codec_id);
  
    if not Assigned(codec) then
  
    begin
  
      Writeln(ErrOutput, 'Codec not found');
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
  
  
    c := avcodec_alloc_context3(codec);
  
    if not Assigned(c) then
  
    begin
  
      Writeln(ErrOutput, 'Could not allocate video codec context');
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
  
  
    (* put sample parameters *)
  
    c.bit_rate := 400000;
  
    (* resolution must be a multiple of two *)
  
    c.width := 352;
  
    c.height := 288;
  
    (* frames per second *)
  
    c.time_base.num := 1;
  
    c.time_base.den := 25;
  
    (* emit one intra frame every ten frames
  
     * check frame pict_type before passing frame
  
     * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
     * then gop_size is ignored and the output of encoder
  
     * will always be I frame irrespective to gop_size
  
     *)
  
    c.gop_size := 10;
  
    c.max_b_frames := 1;
  
    c.pix_fmt := AV_PIX_FMT_YUV420P;
  
  
  
    if codec_id = AV_CODEC_ID_H264 then
  
      av_opt_set(c.priv_data, 'preset', 'slow', 0);
  
  
  
    (* open it *)
  
    if avcodec_open2(c, codec, nil) < 0 then
  
    begin
  
      Writeln(ErrOutput, 'Could not open codec');
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
  
  
    f := FileCreate(filename);
  
    if f = INVALID_HANDLE_VALUE then
  
    begin
  
      Writeln(ErrOutput, Format('Could not open %s', [filename]));
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
  
  
    frame := av_frame_alloc();
  
    if not Assigned(frame) then
  
    begin
  
      Writeln(ErrOutput, 'Could not allocate video frame');
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
    frame.format := Ord(c.pix_fmt);
  
    frame.width  := c.width;
  
    frame.height := c.height;
  
  
  
    (* the image can be allocated by any means and av_image_alloc() is
  
     * just the most convenient way if av_malloc() is to be used *)
  
    ret := av_image_alloc(@frame.data[0], @frame.linesize[0], c.width, c.height,
  
                         c.pix_fmt, 32);
  
    if ret < 0 then
  
    begin
  
      Writeln(ErrOutput, 'Could not allocate raw picture buffer');
  
      ExitCode := 1;
  
      Exit;
  
    end;
  
  
  
    (* encode 1 second of video *)
  
    idx := 1;
  
    for i := 0 to 25 - 1 do
  
    begin
  
      av_init_packet(@pkt);
  
      pkt.data := nil;    // packet data will be allocated by the encoder
  
      pkt.size := 0;
  
  
  
      //fflush(stdout);
  
      (* prepare a dummy image *)
  
      (* Y *)
  
      for y := 0 to c.height - 1 do
  
        for x := 0 to c.width - 1 do
  
          PByte(@PAnsiChar(frame.data[0])[y * frame.linesize[0] + x])^ := x + y + i * 3;
  
  
  
      (* Cb and Cr *)
  
      for y := 0 to c.height div 2 - 1 do
  
        for x := 0 to c.width div 2 - 1 do
  
        begin
  
          PByte(@PAnsiChar(frame.data[1])[y * frame.linesize[1] + x])^ := 128 + y + i * 2;
  
          PByte(@PAnsiChar(frame.data[2])[y * frame.linesize[2] + x])^ := 64 + x + i * 5;
  
        end;
  
  
  
      frame.pts := i;
  
  
  
      (* encode the image *)
  
      ret := avcodec_encode_video2(c, @pkt, frame, @got_output);
  
      if ret < 0 then
  
      begin
  
        Writeln(ErrOutput, 'Error encoding frame');
  
        ExitCode := 1;
  
        Exit;
  
      end;
  
  
  
      if got_output <> 0 then
  
      begin
  
        Writeln(Format('Write frame %d (size=%d)', [idx, pkt.size]));
  
        FileWrite(f, pkt.data^, pkt.size);
  
        av_packet_unref(@pkt);
  
        Inc(idx);
  
      end;
  
    end;
  
  
  
    (* get the delayed frames *)
  
    repeat
  
      //fflush(stdout);
  
  
  
      ret := avcodec_encode_video2(c, @pkt, nil, @got_output);
  
      if ret < 0 then
  
      begin
  
        Writeln(ErrOutput, 'Error encoding frame');
  
        ExitCode := 1;
  
        Exit;
  
      end;
  
  
  
      if got_output <> 0 then
  
      begin
  
        Writeln(Format('Write frame %d (size=%d)', [idx, pkt.size]));
  
        FileWrite(f, pkt.data^, pkt.size);
  
        av_packet_unref(@pkt);
  
        Inc(idx);
  
      end;
  
    until got_output = 0;
  
  
  
    (* add sequence end code to have a real mpeg file *)
  
    FileWrite(f, endcode[0], SizeOf(endcode));
  
    FileClose(f);
  
  
  
    avcodec_close(c);
  
    av_free(c);
  
    av_freep(@frame.data[0]);
  
    av_frame_free(@frame);
  
    Writeln('');
  
  end;

  yes we know this formula, but what should we do with (* Cb and Cr *) loop that goes up to c.height div 2 - 1 and c.width div 2 - 1 ? all our experiments make correct image geometry but incorrect colors... Here is what we have :

  ( Y )
  
      for y := 0 to c.height - 1 do
  
      begin
  
        Line := image.ScanLine[y];
  
        for x := 0 to c.width - 1 do
  
        begin
  
          Yy := Round(Line[x].R*0.29900 + Line[x].G*0.58700 + Line[x].B*0.11400);
  
          PByte(@PAnsiChar(frame.data[0])[y * frame.linesize[0] + x])^ := Yy;
  
        end;
  
      end;
  
      ( Cb and Cr )
  
      for y := 0 to c.height div 2 - 1 do
  
      begin
  
        Pixels := image.ScanLine[y];
  
        for x := 0 to c.width div 2 - 1 do
  
        begin
  
          Cb := Round(Line[x].R  -0.16874 - Line[x].G  0.33126 + Line[x].B * 0.50000) + 128;
  
          Cr := Round(Line[x].R   0.50000 - Line[x].G  0.41869 - Line[x].B * 0.08131) + 64;
  
          PByte(@PAnsiChar(frame.data[1])[y * frame.linesize[1] + x])^ := Cr;
  
          PByte(@PAnsiChar(frame.data[2])[y * frame.linesize[2] + x])^ := Cb;
  
          //PByte(@PAnsiChar(frame.data[1])[y  frame.linesize[1] + x])^ := 128 + y + i  2;
  
          //PByte(@PAnsiChar(frame.data[2])[y  frame.linesize[2] + x])^ := 64 + x + i  5;
  
        end;
  
      end;

  How this should be fixed ?

• duration change after transcode ts

  25 décembre 2017, par Feilong Luo

  i have a problem about transcode with ffmpeg

  i want to cover m3u8 to mp4, so i transcode every ts file first, and then concat them to a mp4, but i found that the duration will be bigger than source file.

  source file is :
  http://oc7iy3eta.bkt.clouddn.com/src_20.ts

  after transcode, test file is :
  http://oc7iy3eta.bkt.clouddn.com/test_20.ts

  i use the command as bellow to change to 5fps, and 400k bitrate :

  sudo ffmpeg -analyzeduration 2147483647 -probesize 2147483647 -nostdin -y -v warning -i ./src_20.ts -threads 3 -movflags faststart -metadata:s:v rotate=0 -chunk_duration 520000 -video_track_timescale 25000 -pix_fmt yuv420p -copytb 1 -vcodec libx264 -b:v 400000 -minrate 400000 -maxrate 400000 -bufsize 500k -force_key_frames "expr:gte(t,n_forced*2)" -vsync 1 -r 5 -s 544*960 -acodec libfaac -async 1 ./test_20.ts

  i use ffprobe command to see video info :

  source file info :

  Duration : 00:00:01.26, start : 28.346989, bitrate : 921 kb/s
  Program 1
  Metadata :
  service_name : Service01
  service_provider : FFmpeg
  Stream #0:0[0x100] : Audio : aac ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 23 kb/s
  Stream #0:1[0x101] : Video : h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 544x960, 10.67 tbr, 90k tbn, 180k tbc

  test file :

  Input #0, mpegts, from ’test_20.ts’ :
  Duration : 00:00:01.62, start : 1.576778, bitrate : 447 kb/s
  Program 1
  Metadata :
  service_name : Service01
  service_provider : FFmpeg
  Stream #0:0[0x100] : Video : h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 544x960, 5 fps, 5 tbr, 90k tbn, 10 tbc
  Stream #0:1[0x101] : Audio : aac ([15][0][0][0] / 0x000F), 44100 Hz, stereo, fltp, 5 kb/s

  =======================================================================

  question

  so , we can see that the duration of src file is 1.26s , but after transcode, the test file is 1.62s.

  why ? can anybody help

• Encoding RGB frames using x264 and AVCodec in C

  6 novembre 2016, par deepwork

  I have RGB24 frames streamed from camera and i want to encode them into h264 ,i found that AVCodec and x264 can do so, the problem is x264 as default accepts YUV420 as input so what i wrote was a program which convert RGB frames to YUV420 .that was by sws_scale function .this works well except that it does not satisfy the required FPS because the converting (RGB->YUV420) takes time.

  This is how i setup my encoder context :

  videoStream->id = 0;
  
  vCodecCtx = videoStream->codec;
  
  
  
  vCodecCtx->coder_type       = AVMEDIA_TYPE_VIDEO;
  
  vCodecCtx->codec_id         = AV_CODEC_ID_H264;
  
  vCodecCtx->bit_rate         = 400000;
  
  vCodecCtx->width            = Width;
  
  vCodecCtx->height           = Height;
  
  vCodecCtx->time_base.den    = FPS;
  
  vCodecCtx->time_base.num    = 1;
  
  //vCodecCtx->time_base      = (AVRational){1,};
  
  vCodecCtx->gop_size         = 12;
  
  vCodecCtx->max_b_frames     = 1;
  
  vCodecCtx->pix_fmt          = AV_PIX_FMT_YUV420P;
  
  
  
  if(formatCtx->oformat->flags & AVFMT_GLOBALHEADER)
  
      vCodecCtx->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
  av_opt_set(vCodecCtx->priv_data, "preset", "ultrafast", 0);
  
  av_opt_set(vCodecCtx->priv_data, "profile", "baseline", AV_OPT_SEARCH_CHILDREN);
  
  
  
  if (avcodec_open2(vCodecCtx, h264Codec, NULL) < 0){
  
      return 0;
  
  }

  when i changes AV_PIX_FMT_YUV420P to AV_PIX_FMT_RGB24 ,avcodec_open2 will fail.
  i read that there is a version of libx264 for RGB called libx264rgb but i even dont know whether i have to rebuild x264 with enabling this option or to download another source or i have to do it programmatically with the first x264 lib.

  the question is how to enable RGB as input to libx264 to use with libavcodec in C .or how to make the encoding or sws_scale more fast .

  Edit :

  How i built ffmpeg :

  NDK=D:/AndroidDev/android-ndk-r9
  
  PLATFORM=$NDK/platforms/android-18/arch-arm/
  
  PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/windows-x86_64
  
  
  
  GENERAL="\
  
  --enable-small \
  
  --enable-cross-compile \
  
  --extra-libs="-lgcc" \
  
  --arch=arm \
  
  --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
  
  --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
  
  --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
  
  --extra-cflags="-I../x264/android/arm/include" \
  
  --extra-ldflags="-L../x264/android/arm/lib" "
  
  
  
  
  
  MODULES="\
  
  --enable-gpl \
  
  --enable-libx264"
  
  
  
  function build_ARMv6
  
  {
  
    ./configure \
  
    --target-os=linux \
  
    --prefix=./android/armeabi \
  
    ${GENERAL} \
  
    --sysroot=$PLATFORM \
  
    --enable-shared \
  
    --disable-static \
  
    --extra-cflags=" -O3 -fpic -fasm -Wno-psabi -fno-short-enums -fno-strict-aliasing -finline-limit=300 -mfloat-abi=softfp -mfpu=vfp -marm -march=armv6" \
  
    --extra-ldflags="-lx264 -Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib -lc -lm -ldl -llog" \
  
    --enable-zlib \
  
    ${MODULES} \
  
    --disable-doc \
  
    --enable-neon
  
  
  
    make clean
  
    make
  
    make install
  
  }
  
  
  
  build_ARMv6
  
  
  
  echo Android ARMEABI builds finished

  How i built x264 :

  NDK=D:/AndroidDev/android-ndk-r9
  
  PLATFORM=$NDK/platforms/android-18/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/windows-x86_64
  
  PREFIX=./android/arm
  
  
  
  function build_one
  
  {
  
    ./configure \
  
    --prefix=$PREFIX \
  
    --enable-static \
  
    --enable-pic \
  
    --host=arm-linux \
  
    --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
    --sysroot=$PLATFORM
  
  
  
    make clean
  
    make
  
    make install
  
  }
  
  
  
  build_one
  
  
  
  echo Android ARM builds finished