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• Why are there multiple timescale specified in a MP4/AVC container file ?

  24 juin 2021, par Lexx32117

  I am currently parsing a MPEG-DASH stream initialization segment (generated by FFMPEG) and I noticed that the timescale is specified at multiple different places in my file :

  


  

  • In the movie header box (mvhd) : 1000

  


  • In the media header box of my video track (mdhd) : 15360

  


  • In the AVC Configuration box (avcC) more precisely in the VUI section of the sequence parameter set NAL unit : 60

  


  


  Why is it specified in so many different places ? Why do they have different values ? Is there a hierarchy in these value ? For example does 60 overrides 15360 and 15360 overrides 1000 ?

  


  Here's the command I used to generate the file I am looking at :

  


  ffmpeg -f v4l2 -pixel_format yuyv422 -vcodec rawvideo -framerate 30 -video_size 640x360 -i /dev/video0 \
        -f dash -remove_at_exit false -use_template true -use_timeline true -streaming true -window_size 5 -extra_window_size 5 -seg_duration 5 -vcodec libx264 -b:v 1M -maxrate 1M -bufsize 2M  -pix_fmt yuv420p -r 30 -s 640x360 -aspect 16:9 /var/www/html/media/live.mpd


  


• problem with "subprocess.Popen" AFTER make .exe file

  1er février 2020, par afcc0060

  im try to convert mp3 to mp4 with ffmpeg (command line)
  everything is well and program runs correctly.
  i have one progressbar and handle it from this function by reading ffmpeg command line output

  cls_wnd.pbar_step(line.lower())

  but after make (single) .exe file with pyinstaller program not run and did not convert anything

          def _cli(self ,cls_wnd ,cmd):
  
              errors = False
  
              cmd_output=""
  
  
  
              line=''
  
              try:
  
                      p = subprocess.Popen(cmd ,stdout=subprocess.PIPE ,
  
                                                stderr=subprocess.STDOUT ,
  
                                                universal_newlines=True ,
  
                                                shell=False ,
  
                                                creationflags = subprocess.CREATE_NO_WINDOW)
  
  
  
                      for line in p.stdout:
  
                              if cls_wnd.bt02.cget('text').lower()!="cancel":
  
                                      p.kill()
  
                                      return cmd_output, True ,'cancel'
  
                              cmd_output+=line
  
                              if line.lower().find('duration:')>-1 or line.lower().find('frame=')<1:
  
                                      cls_wnd.pbar_step(line.lower())
  
                              cls_wnd.root.update()
  
  
  
                      stdoutdata, stderrdata = p.communicate()
  
                      if p.wait() != 0:
  
                              p.kill()
  
                              return cmd_output, True ,line
  
                      p.kill()
  
                      return cmd_output, errors ,' '
  
              except OSError as e:
  
                      p.kill()
  
                      return cmd_output,True,' exit from except '
  
              return '',True,'exit from _cli end'

  cmd is somthnig like this

  cmd='ffmpeg -y -loop 1 -i 1.jpg -i 1.mp3 -c:a copy -c:v libx264 -shortest 1.mp4'

  make .exe file with this command

  pyinstaller -w --onefile  mp3tomp4.py --onefile

  if i dont use’-w’ every thing is well .. but that ugly black cmd-windows shown and i can not close or hide it

• Using ffmpeg dll's from a windows 32 bit app

  8 avril 2020, par Derek

  I am trying to use ffmpeg via dll calls from a win32 app (compiled in clarion)

  



  I transcoded the example file encode_video.c and that worked 100% however I was left with a .h264 file instead of a .mp4 file.

  



  I then transcoded the example muxing.c however it crashes and I am at a loss for options.

  



  Any help would be most appreciated.

  



  Encode_mp4 ROUTINE
! avformat_alloc_output_context2 *******************************************************************************************
file_name = 'myvideo.mp4'
! Try guess format from filename
if CHECK_STACK then ds_SaveStack .
Result = avformat_alloc_output_context2(ThisPtrPtr, 0, NullCString, file_name);
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avformat_alloc_output_context2 Try guess format failed, try mpeg', TRUE)
    CString1 = 'mpeg'
    if CHECK_STACK then ds_SaveStack .
    Result = avformat_alloc_output_context2(ThisPtrPtr, 0, CString1, file_name);
    if CHECK_STACK then ds_TestStack .
    if Result < 0
        ds_OutputDebugString('avformat_alloc_output_context2 failed', TRUE)
        stop('Could not allocate output format context')
        exit
    end
end
formater_ctxt &= (ThisPtrPtr)
!ds_OutputDebugString('formater_ctxt=' & address(formater_ctxt), TRUE)
assert(not(formater_ctxt &= NULL), 'Check AVFormatContext formater_ctxt')
do VerifyFormatContext
assert(formater_ctxt.oformat > 0, 'Check AVFormatContext formater_ctxt.oformat')
formater &= (formater_ctxt.oformat)
do VerifyFormat
ds_OutputDebugString('avformat_alloc_output_context2 OK', TRUE)

! avcodec_find_encoder *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
encoder &= avcodec_find_encoder(formater.video_codec)
if CHECK_STACK then ds_TestStack .
if encoder &= NULL
    ds_OutputDebugString('avcodec_find_encoder failed', TRUE)
    stop('Could not find encoder')
    exit
end
do VerifyEncoder
ds_OutputDebugString('avcodec_find_encoder OK', TRUE)

! avformat_new_stream *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
stream &= avformat_new_stream(formater_ctxt, encoder)
if CHECK_STACK then ds_TestStack .
if stream &= NULL 
    ds_OutputDebugString('avformat_new_stream failed', TRUE)
    stop('Could not create new stream')
    exit
end
do VerifyStream
stream.id = formater_ctxt.nb_streams-1
ds_OutputDebugString('avformat_new_stream OK', TRUE)

! avcodec_alloc_context3 *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
encoder_ctxt &= avcodec_alloc_context3(encoder)
if CHECK_STACK then ds_TestStack .
if encoder_ctxt &= NULL 
    ds_OutputDebugString('avcodec_alloc_context3 failed', TRUE)
    stop('Could not allocate video codec context')
    exit
end
do VerifyEncoderContext
ds_OutputDebugString('avcodec_alloc_context3 OK', TRUE)

! Video settings *******************************************************************************************
do InitVideoSettings

assert(AV_CODEC_FLAG_GLOBAL_HEADER = bshift(1, 22), 'Check AV_CODEC_FLAG_GLOBAL_HEADER')
if band(formater.flags, AVFMT_GLOBALHEADER)
   encoder_ctxt.flags = bor(encoder_ctxt.flags, AV_CODEC_FLAG_GLOBAL_HEADER) !avctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
end

! avcodec_open2 *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
Result = avcodec_open2(encoder_ctxt, encoder, 0)
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avcodec_open2 failed.  Result=' & Result, TRUE)
    stop('Could not open codec')
    exit
end
ds_OutputDebugString('avcodec_open2 OK', TRUE)

! av_frame_alloc *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
frame &= av_frame_alloc();
if CHECK_STACK then ds_TestStack .
if frame &= NULL
    ds_OutputDebugString('av_frame_alloc failed', TRUE)
    stop('Could not allocate video frame')
    exit
end
do VerifyFrame
frame.format = encoder_ctxt.pix_fmt
frame.width = encoder_ctxt.width
frame.height = encoder_ctxt.height
ds_OutputDebugString('av_frame_alloc OK', TRUE)

! av_frame_get_buffer *******************************************************************************************
if CHECK_STACK then ds_SaveStack .
Result = av_frame_get_buffer(frame, 32)
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('av_frame_get_buffer failed', TRUE)
    stop('Could not allocate video frame buffer Error = ' & Result)
    exit
end
do VerifyFrameBuffer
ds_OutputDebugString('av_frame_get_buffer OK', TRUE)

!frame->data offset=0  Array[8] of *int8_t
UseData0 &= (frame.data[1])
UseData1 &= (frame.data[2])
UseData2 &= (frame.data[3])

if CHECK_STACK then ds_SaveStack .
Result = avcodec_parameters_from_context(stream.codecpar, encoder_ctxt);
if CHECK_STACK then ds_TestStack .
if Result < 0
    ds_OutputDebugString('avcodec_parameters_from_context failed', TRUE)
    stop('Could not initialize stream parameters')
    exit
end
ds_OutputDebugString('avcodec_parameters_from_context OK', TRUE)

! av_dump_format *******************************************************************************************
ds_OutputDebugString('before call to av_dump_format  file_name=' & file_name, TRUE)
av_dump_format(formater_ctxt, 0, file_name, 1)


  



  I get a crash at last line - call to av_dump_format()

  



  If I comment this code then I get a crash on the very next lib call :

  



      ! avio_open *******************************************************************************************
if not(band(formater.flags, AVFMT_NOFILE)) 
    ds_OutputDebugString('before call to avio_open  file_name=' & file_name, TRUE)
    ThisInt &= address(formater_ctxt.pb)
    Result = avio_open(ThisInt, file_name, AVIO_FLAG_WRITE)


  



  Strangely if I comment the setup call to av_log_set_callback(my_log_callback) then the crash moves down to the next lib call : avformat_write_header