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• Send sprop-parameter-sets inband rather than in SDP

  21 janvier 2021, par Max

  I am trying to use ffmpeg to stream an MP4 file over rtp. I am sending the stream to a SFU server that will broadcast the stream to users. The clients are expecting to receive an h264 video stream with profile-level-id 42e01f. The issue I'm having is that the video received by the clients does not decode properly (just a black screen). If I transcode the video before sending, then everything works correctly. If I dump the SDP that describes what ffmpeg is sending, there is a distinct difference between the transcoded and non-transcoded version.

  


  For the non-transcoded version, my ffmpeg command looks like

  


  ffmpeg  '-re' \
  '-v' \
  'info' \
  '-protocol_whitelist' \
  'pipe,tls,file,http,https,tcp,rtp' \
  '-i' \
  '-f' 'mp4' \
  'https://storage.googleapis.com/my_bucket/file' \
  '-map' \
  '0:v:0' \
  '-c:v' \
  'copy' \
  '-f' \
  'rtp' \
  '-sdp_file' 'out.sdp' \
  'rtp://142.93.14.110:40425?rtcpport=45155'


  


  When I run this command, out.sdp contains the line

  


  a=fmtp:96 packetization-mode=1; sprop-parameter-sets=Z0LAH9kAUAW7AWoCAgKAAAH0gABdwAeMGSQ=,aMuMsg==; profile-level-id=42C01F


  


  However, if I change -c:v copy to -c:v libx264 -preset ultrafast, then the sdp line changes to a=fmtp:96 packetization-mode=1;. Given that there is no SDP exchange between ffmpeg and my SFU, I think the issue is that ffmpeg needs to be sending the sprops in-band rather than setting them in the sdp. Any help here would be amazing. The other possible issue is that the profile levels are sightly different.

  


• h264_mp4toannexb : Don't forget numOfPictureParameterSets

  14 décembre 2019, par Andreas Rheinhardt

  h264_mp4toannexb : Don't forget numOfPictureParameterSets
  The format of an AVCDecoderConfigurationRecord, the out-of-band
  
  extradata of H.264 in mp4, is as follows : First four bytes containing
  
  version, profile and level, one byte for the length size and one byte
  
  each for the number of SPS, followed by the SPS (each with its own size
  
  field), followed by a byte containing the number of PPS followed by the
  
  PPS with their size fields. While the number of SPS/PPS may be zero, the
  
  bytes containing these numbers are mandatory. Yet the byte containing
  
  the number of PPS has been ignored in two places :
  
  1. In the initial check for whether the extradata can contain an
  
  AVCDecoderConfigurationRecord. The minimum size is 7, not 6.
  
  2. No check is made for whether the extradata ended right after the last
  
  byte of the last SPS of the SPS array. Instead the first byte of the
  
  padding is read as if it were part of the extradata and contained the
  
  number of PPS (namely zero, given that the padding is zeroed). No error
  
  or warning was ever raised.
  
  This has been changed. Such truncated extradata is now considered
  
  invalid ; the check for 2. has been incorporated into the general size
  
  check.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/h264_mp4toannexb_bsf.c

• 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