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• Encoding a growing video file in realtime fails prematurely

  17 janvier 2023, par Macster

  This batch script is repeatedly concatenating video clips from an textfile. The output file is then beeing encoded in realtime into dash format. Unfortunately the realtime encoding will always end prematurely and I can't figure out why. From what I observed, it shouldn't be possible that the realtime encoding would catch up to the concating - which is happening each time after the duration of the clip that was just added - because I'm setting an offset, to when the encoding has to start, via timeout.

  


  I've tried other formats like .mp4 and .h264 and other options, but nothing seems to help. So my assumption is, that there is a conflict when read/write operation is made and these operations overlap at a certain point. But how do I find out when and how to avoid it ? I haven't had the feeling that something was happening at the exact same time, when observing the command promt.

  


  
The screenshot was taken right at failing. As you can see, the concat file queue1.webm is already more than 10 seconds longer than the realtime encoding at its failing position. That's why I don't think it has to do with catching up too fast. It will fail randomly, so one time it fails at 25 seconds and next time it might fail at 2 minutes and 20 seconds.

  


  To avoid the possibility of different video settings causing troubble, I'm using only one video file. I will link it here : BigBuckBunny (Mega NZ) It's a 10 sec snippet from BigBuckBunny. I hope this is legal !? But you can use what ever clip you want.

  


  IMPORTANT : If you try to reproduce the behaviour, please make sure you make at least one entry,
  like file 'bigbuckbunny_webm.webm' in mylist.txt, because adding something if the file is empty is kinda broken :)

  


  So here is the code :

  


  Just the FFMPEG commands :

  


  ffmpeg -f concat -i "mylist.txt" -safe 0  -c copy -f webm -reset_timestamps 1 -streaming 1 -live 1 -y queue1.webm
[..]
ffmpeg -re -i queue1.webm -c copy -map 0:v -use_timeline 1 -use_template 1 -remove_at_exit 0 -window_size 10 -adaptation_sets "id=0,streams=v" -streaming 1 -live 1 -f dash -y queue.mpd


  


  makedir.bat

  


  @ECHO on

:: Create new queue
IF NOT EXIST "queue1.webm" mkfifo "queue1.webm"

setlocal EnableDelayedExpansion

set string=file 'bigbuckbunny_webm.webm'
set video_path=""
SET /a c=0
set file=-1
set file_before=""

:loop
::Get last entry from "mylist.txt"
for /f "delims=" %%a in ('type mylist.txt ^| findstr /b /c:"file"') do (
  set video_path=%%a
)
echo %video_path%

::Insert file 'bigbuckbunny_webm.webm' if mylist.txt is empty.
if "%video_path%" EQU """" (echo %string% >> mylist.txt && set file=%string:~6,-1%) else (set file=%video_path:~6,-1%)

::Insert file 'bigbuckbunny_webm.webm' into mylit.txt if actual entry(%file%) is the same than before(file 'bigbuckbunny_webm.webm').
if "%file%" EQU "%file_before%" (echo. >> mylist.txt && echo %string%>>mylist.txt) 

echo %file%

::Get the video duration
for /f "tokens=1* delims=:" %%a in ('ffmpeg -i %file% 2^>^&1 ^| findstr "Duration"') do (set duration=%%b)
echo %duration%

::Crop format to HH:MM:SS
set duration=%duration:~1,11%
echo %duration%

::Check if seconds are double digits, less than 10, like 09. Then use only 9.
if %duration:~6,1% EQU 0 (
  set /a sec=%duration:~7,1% 
    ) else ( 
        set /a sec=%duration:~6,2%

)
echo %sec%

::Convert duration into seconds
set /a duration=%duration:~0,2%*3600+%duration:~3,2%*60+%sec%
echo %duration%

::echo %duration%

::Increase iteration count.
set /a c=c+1

::Add new clip to queue.
ffmpeg -f concat -i "mylist.txt" -safe 0  -c copy -f webm -reset_timestamps 1 -streaming 1 -live 1 -y queue1.webm

::Start realtime encoding queue1, if a first clip was added.
if !c! EQU 1 (
  start cmd /k "startRealtimeEncoding.bat"
)

::Wait the duration of the inserted video 
timeout /t %duration%

::Set the actual filename as the previous file for the next iteration.
set file_before=%file%

::Stop after c loops.
if !c! NEQ 20 goto loop

echo %c%

endlocal

:end  


  


  startRealtimeEncoding.bat

  


  @ECHO off

timeout /t 5
ffmpeg -re -i queue1.webm -c copy -map 0:v -seg_duration 2 -keyint_min 48 -use_timeline 1 -use_template 1 -remove_at_exit 0 -window_size 10 -adaptation_sets "id=0,streams=v" -streaming 1 -live 1 -f dash -y queue.mpd

:end


  


• FFmpeg - MJPEG decoding - getting different values

  27 décembre 2016, par ahmadh

  I have a set of JPEG frames which I am muxing into an avi, which gives me a mjpeg video. This is the command I run on the console :

  ffmpeg -y -start_number 0 -i %06d.JPEG -codec copy vid.avi

  When I try to demux the video using ffmpeg C api, I get frames which are slightly different in values. Demuxing code looks something like this :

  AVFormatContext* fmt_ctx = NULL;
  
  AVCodecContext* cdc_ctx = NULL;
  
  AVCodec* vid_cdc = NULL;
  
  int ret;
  
  unsigned int height, width;
  
  
  
  ....
  
  // read_nframes is the number of frames to read
  
  output_arr = new unsigned char [height * width * 3 * 
  
                                  sizeof(unsigned char) * read_nframes];
  
  
  
  avcodec_open2(cdc_ctx, vid_cdc, NULL);
  
  
  
  int num_bytes;
  
  uint8_t* buffer = NULL;
  
  const AVPixelFormat out_format = AV_PIX_FMT_RGB24;
  
  
  
  num_bytes = av_image_get_buffer_size(out_format, width, height, 1);
  
  buffer = (uint8_t*)av_malloc(num_bytes * sizeof(uint8_t));
  
  
  
  AVFrame* vid_frame = NULL;
  
  vid_frame = av_frame_alloc();
  
  AVFrame* conv_frame = NULL;
  
  conv_frame = av_frame_alloc();
  
  
  
  av_image_fill_arrays(conv_frame->data, conv_frame->linesize, buffer, 
  
                       out_format, width, height, 1);
  
  
  
  struct SwsContext *sws_ctx = NULL;
  
  sws_ctx = sws_getContext(width, height, cdc_ctx->pix_fmt,
  
                           width, height, out_format,
  
                           SWS_BILINEAR, NULL,NULL,NULL);
  
  
  
  int frame_num = 0;
  
  AVPacket vid_pckt;
  
  while (av_read_frame(fmt_ctx, &vid_pckt) >=0) {
  
      ret = avcodec_send_packet(cdc_ctx, &vid_pckt);
  
      if (ret < 0)
  
          break;
  
  
  
      ret = avcodec_receive_frame(cdc_ctx, vid_frame);
  
      if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
  
          break;
  
      if (ret >= 0) {
  
          // convert image from native format to planar GBR
  
          sws_scale(sws_ctx, vid_frame->data, 
  
                    vid_frame->linesize, 0, vid_frame->height, 
  
                    conv_frame->data, conv_frame->linesize);
  
  
  
          unsigned char* r_ptr = output_arr + 
  
              (height * width * sizeof(unsigned char) * 3 * frame_num);
  
          unsigned char* g_ptr = r_ptr + (height * width * sizeof(unsigned char));
  
          unsigned char* b_ptr = g_ptr + (height * width * sizeof(unsigned char));
  
          unsigned int pxl_i = 0;
  
  
  
          for (unsigned int r = 0; r < height; ++r) {
  
              uint8_t* avframe_r = conv_frame->data[0] + r*conv_frame->linesize[0];
  
              for (unsigned int c = 0; c < width; ++c) {
  
                  r_ptr[pxl_i] = avframe_r[0];
  
                  g_ptr[pxl_i]   = avframe_r[1];
  
                  b_ptr[pxl_i]   = avframe_r[2];
  
                  avframe_r += 3;
  
                  ++pxl_i;
  
              }
  
          }
  
  
  
          ++frame_num;
  
  
  
          if (frame_num >= read_nframes)
  
              break;
  
      }
  
  }
  
  
  
  ...

  In my experience around two-thirds of the pixel values are different, each by +-1 (in a range of [0,255]). I am wondering is it due to some decoding scheme FFmpeg uses for reading JPEG frames ? I tried encoding and decoding png frames, and it works perfectly fine.

  In short my goal is to get the same pixel by pixel values for each JPEG frame as I would I have gotten if I was reading the JPEG images directly. Here is the stand-alone code I used. It includes cmake files to build code, and a couple of jpeg frames with the converted avi file to test this problem. (give —filetype png to test the png decoding).

• Enabling libmp3lame for FFMPEG on elastic beanstalk

  13 octobre 2017, par Adam Sith

  I am trying to enable libmp3lame with FFMPEG in elastic beanstalk (Amazon Redhat Linux machine).

  I am able to successfully install FFMPEG in /ffmpeg.config with the following script :

  # .ebextensions/ffmpeg.config
  
  
  
  packages:
  
    yum:
  
      autoconf: []
  
      automake: []
  
      cmake: []
  
      freetype-devel: []
  
      gcc: []
  
      gcc-c++: []
  
      git: []
  
      libtool: []
  
      make: []
  
      nasm: []
  
      pkgconfig: []
  
      zlib-devel: []
  
  sources:
  
    /usr/local/src: http://ffmpeg.org/releases/ffmpeg-3.2.tar.bz2
  
  commands:
  
    ffmpeg_install:
  
        cwd: /usr/local/src/ffmpeg-3.2
  
        command: sudo ./configure --prefix=/usr && make && make install

  I need to install libmp3lame however. I’ve tried to do this with an --enable-libmp3lame flag and the directions here. The modified script :

  packages:
  
  yum:
  
      autoconf: []
  
      automake: []
  
      cmake: []
  
      freetype-devel: []
  
      gcc: []
  
      gcc-c++: []
  
      git: []
  
      libtool: []
  
      make: []
  
      nasm: []
  
      pkgconfig: []
  
      zlib-devel: []
  
  sources:
  
    /usr/local/src: http://ffmpeg.org/releases/ffmpeg-3.2.tar.bz2
  
  commands:
  
    01-install_libmp3lame:
  
        cwd: /usr/local/src/
  
        command: curl -L -O http://downloads.sourceforge.net/project/lame/lame/3.99/lame-3.99.5.tar.gz && tar xzvf lame-3.99.5.tar.gz && cd lame-3.99.5 && ./configure --prefix="$HOME/ffmpeg_build" --bindir="$HOME/bin" --disable-shared --enable-nasm && make && make install
  
    02-ffmpeg_install:
  
        cwd: /usr/local/src/ffmpeg-3.2
  
        command: sudo ./configure --enable-libmp3lame && --prefix=/usr && make && make install

  This doesn’t work. Command 01-install_libmp3lame completes. Command 02-ffmpeg_install fails because :

  [2017-10-12T20:55:19.324Z] INFO  [24606] - [Application update app-8fe3-123456_7895@111/AppDeployStage0/EbExtensionPreBuild/Infra-EmbeddedPreBuild/prebuild_3_clover_platform/Command 02-ffmpeg_install] : Activity execution failed, because: ERROR: libmp3lame >= 3.98.3 not found

  I have tried installing libmp3lame in /ffmpeg-3.2 and got the same issue.