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• ffmpeg rtp stream has an initial static blurt

  15 décembre 2016, par SephVelut

  I’m using ffmpeg to stream an audio file via rtp. My command is ffmpeg -re -i INPUT -f rtp 'rtp://0.0.0.0:4000'. I’m playback the audio using vlc. The audio plays with decent quality, however there is always an initial spurt of stuttered static sound lasting about 100ms. Other playback devices have the same result so I’m convinced this is isolated to ffmpeg.

  Does anyone have any leads I could follow to investigate why this is happening ? I don’t know where to start.

• Adding an audio track to a video using it's own audio as a source ?

  29 novembre 2016, par user41997

  I have a video file with the following layout :

  • Video
  • DTS audio

  What I would like to do is :

  • Video
  • AAC audio (converted from the DTS source)
  • DTS audio

  I can’t wrap my head around the FFMPEG command I would need to do this, though, since I would need to convert the DTS audio to AAC and then place it ahead of the DTS track. The reason for this is the PS4 media player currently doesn’t let you select audio tracks and it only plays the first one it sees. It doesn’t support DTS audio but I’d like to keep it around.

• libavcodec : ffprobe on file encoded with FFV1 codec reports "read_quant_table error"

  20 novembre 2016, par Ali Alidoust

  I’m using the following code to encode a series of frames into an mkv or avi file with FFV1 encoding :

     HRESULT Session::createContext(LPCSTR filename, UINT width, UINT height, UINT fps_num, UINT fps_den) {
  
      LOG("Exporting to file: ", filename);
  
  
  
      AVCodecID codecId = AV_CODEC_ID_FFV1;
  
      this->pixelFormat = AV_PIX_FMT_YUV420P;
  
  
  
      this->codec = avcodec_find_encoder(codecId);
  
      RET_IF_NULL(this->codec, "Could not create codec", E_FAIL);
  
  
  
      this->oformat = av_guess_format(NULL, filename, NULL);
  
      RET_IF_NULL(this->oformat, "Could not create format", E_FAIL);
  
      this->oformat->video_codec = codecId;
  
      this->width = width;
  
      this->height = height;
  
      this->codecContext = avcodec_alloc_context3(this->codec);
  
      RET_IF_NULL(this->codecContext, "Could not allocate context for the codec", E_FAIL);
  
  
  
      this->codecContext->codec = this->codec;
  
      this->codecContext->codec_id = codecId;
  
  
  
      this->codecContext->pix_fmt = pixelFormat;
  
      this->codecContext->width = this->width;
  
      this->codecContext->height = this->height;
  
      this->codecContext->time_base.num = fps_den;
  
      this->codecContext->time_base.den = fps_num;
  
  
  
      this->codecContext->gop_size = 1;
  
  
  
  
  
      RET_IF_FAILED_AV(avformat_alloc_output_context2(&fmtContext, this->oformat, NULL, NULL), "Could not allocate format context", E_FAIL);
  
      RET_IF_NULL(this->fmtContext, "Could not allocate format context", E_FAIL);
  
  
  
      this->fmtContext->oformat = this->oformat;
  
      this->fmtContext->video_codec_id = codecId;
  
  
  
      this->stream = avformat_new_stream(this->fmtContext, this->codec);
  
      RET_IF_NULL(this->stream, "Could not create new stream", E_FAIL);
  
      this->stream->time_base = this->codecContext->time_base;
  
      RET_IF_FAILED_AV(avcodec_parameters_from_context(this->stream->codecpar, this->codecContext), "Could not convert AVCodecContext to AVParameters", E_FAIL);
  
  
  
      if (this->fmtContext->oformat->flags & AVFMT_GLOBALHEADER)
  
      {
  
          this->codecContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
      }
  
  
  
      av_opt_set_int(this->codecContext->priv_data, "coder", 0, 0);
  
      av_opt_set_int(this->codecContext->priv_data, "context", 1, 0);
  
      av_opt_set_int(this->codecContext->priv_data, "slicecrc", 1, 0);
  
      //av_opt_set_int(this->codecContext->priv_data, "slicecrc", 1, 0);
  
      //av_opt_set_int(this->codecContext->priv_data, "pix_fmt", pixelFormat, 0);
  
  
  
      RET_IF_FAILED_AV(avcodec_open2(this->codecContext, this->codec, NULL), "Could not open codec", E_FAIL);
  
      RET_IF_FAILED_AV(avio_open(&this->fmtContext->pb, filename, AVIO_FLAG_WRITE), "Could not open output file", E_FAIL);
  
      RET_IF_NULL(this->fmtContext->pb, "Could not open output file", E_FAIL);
  
      RET_IF_FAILED_AV(avformat_write_header(this->fmtContext, NULL), "Could not write header", E_FAIL);
  
  
  
      frame = av_frame_alloc();
  
      RET_IF_NULL(frame, "Could not allocate frame", E_FAIL);
  
      frame->format = this->codecContext->pix_fmt;
  
      frame->width = width;
  
      frame->height = height;
  
      return S_OK;
  
  }
  
  
  
  HRESULT Session::writeFrame(IMFSample * pSample) {
  
      IMFMediaBuffer *mediaBuffer = NULL;
  
      BYTE *pDataNV12 = NULL;
  
      DWORD length;
  
  
  
      RET_IF_FAILED(pSample->ConvertToContiguousBuffer(&mediaBuffer), "Could not convert IMFSample to contagiuous buffer", E_FAIL);
  
      RET_IF_FAILED(mediaBuffer->GetCurrentLength(&length), "Could not get buffer length", E_FAIL);
  
      RET_IF_FAILED(mediaBuffer->Lock(&pDataNV12, NULL, NULL), "Could not lock the buffer", E_FAIL);
  
      BYTE *pDataYUV420P = new BYTE[length];
  
      this->convertNV12toYUV420P(pDataNV12, pDataYUV420P, this->width, this->height);
  
      RET_IF_FAILED(av_image_fill_arrays(frame->data, frame->linesize, pDataYUV420P, pixelFormat, this->width, this->height, 1), "Could not fill the frame with data from the buffer", E_FAIL);
  
      LOG_IF_FAILED(mediaBuffer->Unlock(), "Could not unlock the buffer");
  
  
  
      frame->pts = av_rescale_q(this->pts++, this->codecContext->time_base, this->stream->time_base);
  
  
  
      AVPacket pkt;
  
  
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;
  
      pkt.size = 0;
  
  
  
      RET_IF_FAILED_AV(avcodec_send_frame(this->codecContext, frame), "Could not send the frame to the encoder", E_FAIL);
  
      delete[] pDataYUV420P;
  
      if (SUCCEEDED(avcodec_receive_packet(this->codecContext, &pkt))) {
  
          RET_IF_FAILED_AV(av_interleaved_write_frame(this->fmtContext, &pkt), "Could not write the received packet.", E_FAIL);
  
      }
  
  
  
      av_packet_unref(&pkt);
  
  
  
      return S_OK;
  
  }
  
  
  
  HRESULT Session::endSession() {
  
      LOG("Ending session...");
  
  
  
      LOG("Closing files...")
  
      LOG_IF_FAILED_AV(av_write_trailer(this->fmtContext), "Could not finalize the output file.");
  
      LOG_IF_FAILED_AV(avio_close(this->fmtContext->pb), "Could not close the output file.");
  
      LOG_IF_FAILED_AV(avcodec_close(this->codecContext), "Could not close the codec.");
  
      av_free(this->codecContext);
  
      LOG("Done.")
  
      return S_OK;
  
  }

  The problem is that the generated file is not playable in either VLC or MPC-HC. However, MPC-HC reports following info in file properties :

  General
  
  Unique ID                      : 202978442142665779317960161865934977227 (0x98B439D9BE859109BD5EC00A62A238CB)
  
  Complete name                  : T:\Test.mkv
  
  Format                         : Matroska
  
  Format version                 : Version 4 / Version 2
  
  File size                      : 24.6 MiB
  
  Duration                       : 147ms
  
  Overall bit rate               : 1 401 Mbps
  
  Writing application            : Lavf57.57.100
  
  Writing library                : Lavf57.57.100
  
  
  
  Video
  
  ID                             : 1
  
  Format                         : FFV1
  
  Format version                 : Version 0
  
  Codec ID                       : V_MS/VFW/FOURCC / FFV1
  
  Duration                       : 147ms
  
  Width                          : 1 280 pixels
  
  Height                         : 720 pixels
  
  Display aspect ratio           : 16:9
  
  Frame rate mode                : Constant
  
  Frame rate                     : 1 000.000 fps
  
  Color space                    : YUV
  
  Chroma subsampling             : 4:2:0
  
  Bit depth                      : 8 bits
  
  Compression mode               : Lossless
  
  Default                        : Yes
  
  Forced                         : No
  
  DURATION                       : 00:00:00.147000000
  
  coder_type                     : Golomb Rice

  Something to note is that it reports 1000 FPS which is weird since I’ve set AVCodecContext::time_base in the code.

  UPDATE 1 :

  I managed to set the correct fps by setting time_base property of the stream :

  this->stream->time_base.den = fps_num;
  
  this->stream->time_base.num = fps_den;

  VLC plays the output file but it shows VLC logo instead of the video, as if there is no video stream in the file.

  UPDATE 2 :

  Cleaned up the code. Now if I set codecId = AV_CODEC_ID_MPEG2VIDEO the output file is valid and is played in both VLC and MPC-HC. Using ffprobe on the file with FFV1 encoding yields the following result :

  C:\root\apps\ffmpeg>ffprobe.exe t:\test.avi
  
  ffprobe version 3.2 Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 5.4.0 (GCC)
  
    configuration: --disable-static --enable-shared --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-libebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  
    libavutil      55. 34.100 / 55. 34.100
  
    libavcodec     57. 64.100 / 57. 64.100
  
    libavformat    57. 56.100 / 57. 56.100
  
    libavdevice    57.  1.100 / 57.  1.100
  
    libavfilter     6. 65.100 /  6. 65.100
  
    libswscale      4.  2.100 /  4.  2.100
  
    libswresample   2.  3.100 /  2.  3.100
  
    libpostproc    54.  1.100 / 54.  1.100
  
  [ffv1 @ 00000000006b83a0] read_quant_table error
  
  Input #0, avi, from 't:\test.avi':
  
    Metadata:
  
      encoder         : Lavf57.56.100
  
    Duration: 00:00:04.94, start: 0.000000, bitrate: 107005 kb/s
  
      Stream #0:0: Video: ffv1 (FFV1 / 0x31564646), yuv420p, 1280x720, 107717 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc