Recherche avancée

Sur d’autres sites (3162)

• H.264 muxed to MP4 using libavformat not playing back

  14 mai 2015, par Brad Mitchell

  I am trying to mux H.264 data into a MP4 file. There appear to be no errors in saving this H.264 Annex B data out to an MP4 file, but the file fails to playback.

  I’ve done a binary comparison on the files and the issue seems to be somewhere in what is being written to the footer (trailer) of the MP4 file.

  I suspect it has to be something with the way the stream is being created or something.

  Init :

  AVOutputFormat* fmt = av_guess_format( 0, "out.mp4", 0 );
  
  oc = avformat_alloc_context();
  
  oc->oformat = fmt;
  
  strcpy(oc->filename, filename);

  Part of this prototype app I have is creating a png file for each IFrame. So when the first IFrame is encountered, I create the video stream and write the av header etc :

  void addVideoStream(AVCodecContext* decoder)
  
  {
  
      videoStream = av_new_stream(oc, 0);
  
      if (!videoStream)
  
      {
  
           cout << "ERROR creating video stream" << endl;
  
           return;        
  
      }
  
      vi = videoStream->index;    
  
      videoContext = videoStream->codec;      
  
      videoContext->codec_type = AVMEDIA_TYPE_VIDEO;
  
      videoContext->codec_id = decoder->codec_id;
  
      videoContext->bit_rate = 512000;
  
      videoContext->width = decoder->width;
  
      videoContext->height = decoder->height;
  
      videoContext->time_base.den = 25;
  
      videoContext->time_base.num = 1;    
  
      videoContext->gop_size = decoder->gop_size;
  
      videoContext->pix_fmt = decoder->pix_fmt;       
  
  
  
      if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  
          videoContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      av_dump_format(oc, 0, filename, 1);
  
  
  
      if (!(oc->oformat->flags & AVFMT_NOFILE))
  
      {
  
          if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
  
          cout << "Error opening file" << endl;
  
      }
  
      avformat_write_header(oc, NULL);
  
  }

  I write packets out :

  unsigned char* data = block->getData();
  
  unsigned char videoFrameType = data[4];
  
  int dataLen = block->getDataLen();
  
  
  
  // store pps
  
  if (videoFrameType == 0x68)
  
  {
  
      if (ppsFrame != NULL)
  
      {
  
          delete ppsFrame; ppsFrameLength = 0; ppsFrame = NULL;
  
      }
  
      ppsFrameLength = block->getDataLen();
  
      ppsFrame = new unsigned char[ppsFrameLength];
  
      memcpy(ppsFrame, block->getData(), ppsFrameLength);
  
  }
  
  else if (videoFrameType == 0x67)
  
  {
  
      // sps
  
      if (spsFrame != NULL)
  
      {
  
          delete spsFrame; spsFrameLength = 0; spsFrame = NULL;
  
  }
  
      spsFrameLength = block->getDataLen();
  
      spsFrame = new unsigned char[spsFrameLength];
  
      memcpy(spsFrame, block->getData(), spsFrameLength);                 
  
  }                                           
  
  
  
  if (videoFrameType == 0x65 || videoFrameType == 0x41)
  
  {
  
      videoFrameNumber++;
  
  }
  
  if (videoFrameType == 0x65)
  
  {
  
      decodeIFrame(videoFrameNumber, spsFrame, spsFrameLength, ppsFrame, ppsFrameLength, data, dataLen);
  
  }
  
  
  
  if (videoStream != NULL)
  
  {
  
      AVPacket pkt = { 0 };
  
      av_init_packet(&pkt);
  
      pkt.stream_index = vi;
  
      pkt.flags = 0;                      
  
      pkt.pts = pkt.dts = 0;                                  
  
  
  
      if (videoFrameType == 0x65)
  
      {
  
          // combine the SPS PPS & I frames together
  
          pkt.flags |= AV_PKT_FLAG_KEY;                                                   
  
          unsigned char* videoFrame = new unsigned char[spsFrameLength+ppsFrameLength+dataLen];
  
          memcpy(videoFrame, spsFrame, spsFrameLength);
  
          memcpy(&videoFrame[spsFrameLength], ppsFrame, ppsFrameLength);
  
          memcpy(&videoFrame[spsFrameLength+ppsFrameLength], data, dataLen);
  
  
  
          // overwrite the start code (00 00 00 01 with a 32-bit length)
  
          setLength(videoFrame, spsFrameLength-4);
  
          setLength(&videoFrame[spsFrameLength], ppsFrameLength-4);
  
          setLength(&videoFrame[spsFrameLength+ppsFrameLength], dataLen-4);
  
          pkt.size = dataLen + spsFrameLength + ppsFrameLength;
  
          pkt.data = videoFrame;
  
          av_interleaved_write_frame(oc, &pkt);
  
          delete videoFrame; videoFrame = NULL;
  
      }
  
      else if (videoFrameType != 0x67 && videoFrameType != 0x68)
  
      {   
  
          // Send other frames except pps & sps which are caught and stored                   
  
          pkt.size = dataLen;
  
          pkt.data = data;
  
          setLength(data, dataLen-4);                     
  
          av_interleaved_write_frame(oc, &pkt);
  
      }

  Finally to close the file off :

  av_write_trailer(oc);
  
  int i = 0;
  
  for (i = 0; i < oc->nb_streams; i++)
  
  {
  
      av_freep(&oc->streams[i]->codec);
  
      av_freep(&oc->streams[i]);      
  
  }
  
  
  
  if (!(oc->oformat->flags & AVFMT_NOFILE))
  
  {
  
      avio_close(oc->pb);
  
  }
  
  av_free(oc);

  If I take the H.264 data alone and convert it :

  ffmpeg -i recording.h264 -vcodec copy recording.mp4

  All but the "footer" of the files are the same.

  Output from my program :
  readrec recording.tcp out.mp4
  ** START * 01-03-2013 14:26:01 180000
  Output #0, mp4, to ’out.mp4’ :
  Stream #0:0 : Video : h264, yuv420p, 352x288, q=2-31, 512 kb/s, 90k tbn, 25 tbc
  * END ** 01-03-2013 14:27:01 102000
  Wrote 1499 video frames.

  If I try to convert using ffmpeg the MP4 file created using CODE :

  ffmpeg -i out.mp4 -vcodec copy out2.mp4
  
  ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
  
        built on Mar  7 2013 12:49:22 with suncc 0x5110
  
        configuration: --extra-cflags=-KPIC -g --disable-mmx
  
        --disable-protocol=udp --disable-encoder=nellymoser --cc=cc --cxx=CC
  
  libavutil      51. 54.100 / 51. 54.100
  
  libavcodec     54. 23.100 / 54. 23.100
  
  libavformat    54.  6.100 / 54.  6.100
  
  libavdevice    54.  0.100 / 54.  0.100
  
  libavfilter     2. 77.100 /  2. 77.100
  
  libswscale      2.  1.100 /  2.  1.100
  
  libswresample   0. 15.100 /  0. 15.100
  
  h264 @ 12eaac0] no frame!
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 23 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 74 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 64 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 34 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 49 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 24 times
  
  [h264 @ 12eaac0] Partitioned H.264 support is incomplete
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 23 times
  
  [h264 @ 12eaac0] sps_id out of range
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 148 times
  
  [h264 @ 12eaac0] sps_id (32) out of range
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 33 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 128 times
  
  [h264 @ 12eaac0] sps_id (32) out of range
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 3 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 3 times
  
  [h264 @ 12eaac0] slice type too large (0) at 0 0
  
  [h264 @ 12eaac0] decode_slice_header error
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 309 times
  
  [h264 @ 12eaac0] sps_id (32) out of range
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 192 times
  
  [h264 @ 12eaac0] Partitioned H.264 support is incomplete
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 73 times
  
  [h264 @ 12eaac0] sps_id (32) out of range
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 99 times
  
  [h264 @ 12eaac0] sps_id (32) out of range
  
      Last message repeated 1 times
  
  [h264 @ 12eaac0] no frame!
  
      Last message repeated 197 times
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 12e3100] decoding for stream 0 failed
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 12e3100] Could not find codec parameters
  
  (Video: h264 (avc1 / 0x31637661), 393539 kb/s)
  
  out.mp4: could not find codec parameters

  I really do not know where the issue is, except it has to be something to do with the way the streams are being set up. I’ve looked at bits of code from where other people are doing a similar thing, and tried to use this advice in setting up the streams, but to no avail !

  ---

  The final code which gave me a H.264/AAC muxed (synced) file is as follows. First a bit of background information. The data is coming from an IP camera. The data is presented via a 3rd party API as video/audio packets. The video packets are presented as the RTP payload data (no header) and consist of NALU’s that are reconstructed and converted to H.264 video in Annex B format. AAC audio is presented as raw AAC and is converted to adts format to enable playback. These packets have been put into a bitstream format that allows the transmission of the timestamp (64 bit milliseconds since Jan 1 1970) along with a few other things.

  This is more or less a prototype and is not clean in any respects. It probably leaks bad. I do however, hope this helps anyone else out trying to achieve something similar to what I am.

  Globals :

  AVFormatContext* oc = NULL;
  
  AVCodecContext* videoContext = NULL;
  
  AVStream* videoStream = NULL;
  
  AVCodecContext* audioContext = NULL;
  
  AVStream* audioStream = NULL;
  
  AVCodec* videoCodec = NULL;
  
  AVCodec* audioCodec = NULL;
  
  int vi = 0;  // Video stream
  
  int ai = 1;  // Audio stream
  
  
  
  uint64_t firstVideoTimeStamp = 0;
  
  uint64_t firstAudioTimeStamp = 0;
  
  int audioStartOffset = 0;
  
  
  
  char* filename = NULL;
  
  
  
  Boolean first = TRUE;
  
  
  
  int videoFrameNumber = 0;
  
  int audioFrameNumber = 0;

  Main :

  int main(int argc, char* argv[])
  
  {
  
      if (argc != 3)
  
      {   
  
          cout &lt;&lt; argv[0] &lt;&lt; " <stream playback="playback" file="file"> <output mp4="mp4" file="file">" &lt;&lt; endl;
  
          return 0;
  
      }
  
      char* input_stream_file = argv[1];
  
      filename = argv[2];
  
  
  
      av_register_all();    
  
  
  
      fstream inFile;
  
      inFile.open(input_stream_file, ios::in);
  
  
  
      // Used to store the latest pps &amp; sps frames
  
      unsigned char* ppsFrame = NULL;
  
      int ppsFrameLength = 0;
  
      unsigned char* spsFrame = NULL;
  
      int spsFrameLength = 0;
  
  
  
      // Setup MP4 output file
  
      AVOutputFormat* fmt = av_guess_format( 0, filename, 0 );
  
      oc = avformat_alloc_context();
  
      oc->oformat = fmt;
  
      strcpy(oc->filename, filename);
  
  
  
      // Setup the bitstream filter for AAC in adts format.  Could probably also achieve
  
      // this by stripping the first 7 bytes!
  
      AVBitStreamFilterContext* bsfc = av_bitstream_filter_init("aac_adtstoasc");
  
      if (!bsfc)
  
      {       
  
          cout &lt;&lt; "Error creating adtstoasc filter" &lt;&lt; endl;
  
          return -1;
  
      }
  
  
  
      while (inFile.good())
  
      {
  
          TcpAVDataBlock* block = new TcpAVDataBlock();
  
          block->readStruct(inFile);
  
          DateTime dt = block->getTimestampAsDateTime();
  
          switch (block->getPacketType())
  
          {
  
              case TCP_PACKET_H264:
  
              {       
  
                  if (firstVideoTimeStamp == 0)
  
                      firstVideoTimeStamp = block->getTimeStamp();
  
                  unsigned char* data = block->getData();
  
                  unsigned char videoFrameType = data[4];
  
                  int dataLen = block->getDataLen();
  
  
  
                  // pps
  
                  if (videoFrameType == 0x68)
  
                  {
  
                      if (ppsFrame != NULL)
  
                      {
  
                          delete ppsFrame; ppsFrameLength = 0;
  
                          ppsFrame = NULL;
  
                      }
  
                      ppsFrameLength = block->getDataLen();
  
                      ppsFrame = new unsigned char[ppsFrameLength];
  
                      memcpy(ppsFrame, block->getData(), ppsFrameLength);
  
                  }
  
                  else if (videoFrameType == 0x67)
  
                  {
  
                      // sps
  
                      if (spsFrame != NULL)
  
                      {
  
                          delete spsFrame; spsFrameLength = 0;
  
                          spsFrame = NULL;
  
                      }
  
                      spsFrameLength = block->getDataLen();
  
                      spsFrame = new unsigned char[spsFrameLength];
  
                      memcpy(spsFrame, block->getData(), spsFrameLength);                   
  
                  }                                           
  
  
  
                  if (videoFrameType == 0x65 || videoFrameType == 0x41)
  
                  {
  
                      videoFrameNumber++;
  
                  }
  
                  // Extract a thumbnail for each I-Frame
  
                  if (videoFrameType == 0x65)
  
                  {
  
                      decodeIFrame(h264, spsFrame, spsFrameLength, ppsFrame, ppsFrameLength, data, dataLen);
  
                  }
  
                  if (videoStream != NULL)
  
                  {
  
                      AVPacket pkt = { 0 };
  
                      av_init_packet(&amp;pkt);
  
                      pkt.stream_index = vi;
  
                      pkt.flags = 0;           
  
                      pkt.pts = videoFrameNumber;
  
                      pkt.dts = videoFrameNumber;           
  
                      if (videoFrameType == 0x65)
  
                      {
  
                          pkt.flags = 1;                           
  
  
  
                          unsigned char* videoFrame = new unsigned char[spsFrameLength+ppsFrameLength+dataLen];
  
                          memcpy(videoFrame, spsFrame, spsFrameLength);
  
                          memcpy(&amp;videoFrame[spsFrameLength], ppsFrame, ppsFrameLength);
  
  
  
                          memcpy(&amp;videoFrame[spsFrameLength+ppsFrameLength], data, dataLen);
  
                          pkt.data = videoFrame;
  
                          av_interleaved_write_frame(oc, &amp;pkt);
  
                          delete videoFrame; videoFrame = NULL;
  
                      }
  
                      else if (videoFrameType != 0x67 &amp;&amp; videoFrameType != 0x68)
  
                      {                       
  
                          pkt.size = dataLen;
  
                          pkt.data = data;
  
                          av_interleaved_write_frame(oc, &amp;pkt);
  
                      }                       
  
                  }
  
                  break;
  
              }
  
  
  
          case TCP_PACKET_AAC:
  
  
  
              if (firstAudioTimeStamp == 0)
  
              {
  
                  firstAudioTimeStamp = block->getTimeStamp();
  
                  uint64_t millseconds_difference = firstAudioTimeStamp - firstVideoTimeStamp;
  
                  audioStartOffset = millseconds_difference * 16000 / 1000;
  
                  cout &lt;&lt; "audio offset: " &lt;&lt; audioStartOffset &lt;&lt; endl;
  
              }
  
  
  
              if (audioStream != NULL)
  
              {
  
                  AVPacket pkt = { 0 };
  
                  av_init_packet(&amp;pkt);
  
                  pkt.stream_index = ai;
  
                  pkt.flags = 1;           
  
                  pkt.pts = audioFrameNumber*1024;
  
                  pkt.dts = audioFrameNumber*1024;
  
                  pkt.data = block->getData();
  
                  pkt.size = block->getDataLen();
  
                  pkt.duration = 1024;
  
  
  
                  AVPacket newpacket = pkt;                       
  
                  int rc = av_bitstream_filter_filter(bsfc, audioContext,
  
                      NULL,
  
                      &amp;newpacket.data, &amp;newpacket.size,
  
                      pkt.data, pkt.size,
  
                      pkt.flags &amp; AV_PKT_FLAG_KEY);
  
  
  
                  if (rc >= 0)
  
                  {
  
                      //cout &lt;&lt; "Write audio frame" &lt;&lt; endl;
  
                      newpacket.pts = audioFrameNumber*1024;
  
                      newpacket.dts = audioFrameNumber*1024;
  
                      audioFrameNumber++;
  
                      newpacket.duration = 1024;                   
  
  
  
                      av_interleaved_write_frame(oc, &amp;newpacket);
  
                      av_free_packet(&amp;newpacket);
  
                  }   
  
                  else
  
                  {
  
                      cout &lt;&lt; "Error filtering aac packet" &lt;&lt; endl;
  
  
  
                  }
  
              }
  
              break;
  
  
  
          case TCP_PACKET_START:
  
              break;
  
  
  
          case TCP_PACKET_END:
  
              break;
  
          }
  
          delete block;
  
      }
  
      inFile.close();
  
  
  
      av_write_trailer(oc);
  
      int i = 0;
  
      for (i = 0; i &lt; oc->nb_streams; i++)
  
      {
  
          av_freep(&amp;oc->streams[i]->codec);
  
          av_freep(&amp;oc->streams[i]);       
  
      }
  
  
  
      if (!(oc->oformat->flags &amp; AVFMT_NOFILE))
  
      {
  
          avio_close(oc->pb);
  
      }
  
  
  
      av_free(oc);
  
  
  
      delete spsFrame; spsFrame = NULL;
  
      delete ppsFrame; ppsFrame = NULL;
  
  
  
      cout &lt;&lt; "Wrote " &lt;&lt; videoFrameNumber &lt;&lt; " video frames." &lt;&lt; endl;
  
  
  
      return 0;
  
  }
  
  </output></stream>

  The stream stream/codecs are added and the header is created in a function called addVideoAndAudioStream(). This function is called from decodeIFrame() so there are a few assumptions (which aren’t necessarily good)
  1. A video packet comes first
  2. AAC is present

  The decodeIFrame was kind of a separate prototype by where I was creating a thumbnail for each I Frame. The code to generate thumbnails was from : https://gnunet.org/svn/Extractor/src/plugins/thumbnailffmpeg_extractor.c

  The decodeIFrame function passes an AVCodecContext into addVideoAudioStream :

  void addVideoAndAudioStream(AVCodecContext* decoder = NULL)
  
  {
  
      videoStream = av_new_stream(oc, 0);
  
      if (!videoStream)
  
      {
  
          cout << "ERROR creating video stream" << endl;
  
          return;       
  
      }
  
      vi = videoStream->index;   
  
      videoContext = videoStream->codec;       
  
      videoContext->codec_type = AVMEDIA_TYPE_VIDEO;
  
      videoContext->codec_id = decoder->codec_id;
  
      videoContext->bit_rate = 512000;
  
      videoContext->width = decoder->width;
  
      videoContext->height = decoder->height;
  
      videoContext->time_base.den = 25;
  
      videoContext->time_base.num = 1;
  
      videoContext->gop_size = decoder->gop_size;
  
      videoContext->pix_fmt = decoder->pix_fmt;       
  
  
  
      audioStream = av_new_stream(oc, 1);
  
      if (!audioStream)
  
      {
  
          cout << "ERROR creating audio stream" << endl;
  
          return;
  
      }
  
      ai = audioStream->index;
  
      audioContext = audioStream->codec;
  
      audioContext->codec_type = AVMEDIA_TYPE_AUDIO;
  
      audioContext->codec_id = CODEC_ID_AAC;
  
      audioContext->bit_rate = 64000;
  
      audioContext->sample_rate = 16000;
  
      audioContext->channels = 1;
  
  
  
      if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  
      {
  
          videoContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
          audioContext->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
      }
  
  
  
      av_dump_format(oc, 0, filename, 1);
  
  
  
      if (!(oc->oformat->flags & AVFMT_NOFILE))
  
      {
  
          if (avio_open(&oc->pb, filename, AVIO_FLAG_WRITE) < 0) {
  
              cout << "Error opening file" << endl;
  
          }
  
      }
  
  
  
      avformat_write_header(oc, NULL);
  
  }

  As far as I can tell, a number of assumptions didn’t seem to matter, for example :
  1. Bit Rate. The actual video bit rate was 262k whereas I specified 512kbit
  2. AAC channels. I specified mono, although the actual output was Stereo from memory

  You would still need to know what the frame rate (time base) is for the video & audio.

  Contrary to a lot of other examples, when setting pts & dts on the video packets, it was not playable. I needed to know the time base (25fps) and then set the pts & dts according to that time base, i.e. first frame = 0 (PPS, SPS, I), second frame = 1 (intermediate frame, whatever its called ;)).

  AAC I also had to make the assumption that it was 16000 hz. 1024 samples per AAC packet (You can also have AAC @ 960 samples I think) to determine the audio "offset". I added this to the pts & dts. So the pts/dts are the sample number that it is to played back at. You also need to make sure that the duration of 1024 is set in the packet before writing also.

  —

  I have found additionally today that Annex B isn’t really compatible with any other player so AVCC format should really be used.

  These URLS helped :
  Problem to Decode H264 video over RTP with ffmpeg (libavcodec)
  http://aviadr1.blogspot.com.au/2010/05/h264-extradata-partially-explained-for.html

  When constructing the video stream, I filled out the extradata & extradata_size :

  // Extradata contains PPS & SPS for AVCC format
  
  int extradata_len = 8 + spsFrameLen-4 + 1 + 2 + ppsFrameLen-4;
  
  videoContext->extradata = (uint8_t*)av_mallocz(extradata_len);
  
  videoContext->extradata_size = extradata_len;
  
  videoContext->extradata[0] = 0x01;
  
  videoContext->extradata[1] = spsFrame[4+1];
  
  videoContext->extradata[2] = spsFrame[4+2];
  
  videoContext->extradata[3] = spsFrame[4+3];
  
  videoContext->extradata[4] = 0xFC | 3;
  
  videoContext->extradata[5] = 0xE0 | 1;
  
  int tmp = spsFrameLen - 4;
  
  videoContext->extradata[6] = (tmp >> 8) & 0x00ff;
  
  videoContext->extradata[7] = tmp & 0x00ff;
  
  int i = 0;
  
  for (i=0;iextradata[8+i] = spsFrame[4+i];
  
  videoContext->extradata[8+tmp] = 0x01;
  
  int tmp2 = ppsFrameLen-4;   
  
  videoContext->extradata[8+tmp+1] = (tmp2 >> 8) & 0x00ff;
  
  videoContext->extradata[8+tmp+2] = tmp2 & 0x00ff;
  
  for (i=0;iextradata[8+tmp+3+i] = ppsFrame[4+i];

  When writing out the frames, don’t prepend the SPS & PPS frames, just write out the I Frame & P frames. In addition, replace the Annex B start code contained in the first 4 bytes (0x00 0x00 0x00 0x01) with the size of the I/P frame.

• Investigating Steam for Linux

  1er mars 2013, par Multimedia Mike — Game Hacking

  Valve recently released the final, public version of their Steam client for Linux, and the Linux world rejoiced. At least, it probably did. The announcement was 2 weeks ago on Valentine’s Day and I had other things on my mind, so I missed any fanfare. When framed in this manner, the announcement timing becomes suspect– it’s as though Linux enthusiasts would have plenty of time that day or something.

  
  
  

  Taming the Frontier
  Speculation about a Linux Steam client had been kicking around for nearly as long as Steam has existed. However, sometime last year, the rumors became more substantive.

  I naturally wondered how to port something like Steam to Linux. I have some experience with trying to make a necessarily binary-only program that runs on Linux. I’m fairly well-versed in the assorted technical challenges that one might face when attempting such a feat. Because of this, whenever I hear rumors that a company might be entertaining the notion of porting a major piece of proprietary software to Linux, my instinctive reflex is, “What ?! Why, you fools ?! Save yourselves !”

  At least, that’s how it used to be. The proposal of developing a proprietary binary for Linux has been rendered considerably less insane by a few developments, for example :

  1. The rise of Ubuntu Linux as a quasi de facto standard for desktop Linux computing
  2. The increasing homogeneity in personal desktop computing technology

  What I would like to know is how the Steam client runs on Linux. Does it rely on any libraries being present on the system ? Or does it bring its own ? The latter is a trick that proprietary programs can use– transport all of the shared libraries that the main program binary depends upon, install them someplace out of the way on the filesystem, probably in /opt, and then make the main program a shell script which sets a preload path to rely on the known quantity libraries instead of the copies already on the system.

  Downloading and Installing the Client
  For this exercise, I installed x86_64 desktop Ubuntu 12.04 Linux on a l33t gaming rig that was totally top of the line about 5 years ago, and that someone didn’t want anymore and handed down to me recently. So it should be ideal for this project.

  At first, I was blown away– the Linux client is in a .deb package that is less than 2 MB large. I unpacked the steam.deb file and found a bunch of support libraries — mostly X11 and standard C/C++ runtimes. Just as I suspected. Still, I can’t believe how small the thing is. However, my amazement quickly abated when I actually ran Steam and saw this :

  
  
  

  So it turns out steam.db is just the installer program which immediately proceeds to download an additional 160+ MB of data. So there’s actually a lot more information to possibly sift through.
  
  Another component of the installation is to basically run a big ‘apt-get install’ command to make sure a bunch of required packages are installed :

  
  
  

  After all these installation steps, the client was ready to run. However, whenever I tried to do so, I got this dialog which would cause Steam to close when the dialog was dismissed.

  
  
  

  Not a huge deal ; later NVIDIA drivers are fairly straightforward to install on Ubuntu Linux. After a few minutes of downloading, installing and restarting X, Steam ran with minimal complaint (it still had some issue regarding the video drivers but didn’t seem to consider it a deal-breaker).

  Using Steam on Linux

  So here’s Steam running on Linux :

  
  
  

  If you have experience with using Steam on Windows or Mac, you might observe that it looks exactly the same. I don’t have a very expansive library of games (I only started using Steam because purchasing a few computer components a few years ago entitled me to some free Steam downloads of some of the games on the list in the screenshot). I didn’t really expect any of the games to have Linux versions yet, but it turns out that the indie darling FTL : Faster Than Light has been ported to Linux. FTL was a much-heralded Kickstarter success story and sounded like something I wanted to support. I purchased this from Steam shortly after its release last year and was able to download the Linux version at no additional cost with a single click.

  It runs natively on Linux (note the Ubuntu desktop window decorations) :

  
  
  

  You might notice from the main Steam client that, despite purchasing FTL about a 1/2 year ago and starting it up at least a 1/2 dozen times, I haven’t really invested a whole lot of time into it. I only managed to get about 2 minutes further this time :

  
  
  

  What can I say ? This game just bores me to tears. It’s frustrating because I know that this is one of the cool games that all real gamers are supposed to like, but I practically catch myself nodding off every time I try to run through the tutorial. It’s strange to think that I’ve invested far more time into games that offer considerably less stimulation. That’s probably because I had far more free time compared to gaming options during those times.

  But that’s neither here nor there. We’ll file this under “games that aren’t for me.” I’m glad that people like FTL and a little indie underdog has met with such success. And I’m pleased that Steam on Linux works. It’s native and the games are also native, which is all quite laudable (there was speculation that everything would just be running on top of a Wine layer).

  Deeper Analysis
  So I set out wondering how Steam was able to create a proprietary program that would satisfy a large enough cross-section of Linux users (i.e., on different platforms and distros). Answer : well, they didn’t, per the stated requirements. The installation is only tuned to work on Ubuntu 12.04. However, it works on both 32- and 64-bit platforms, the only 2 desktop CPU platforms that matter these days (unless ARM somehow makes inroads on the desktop). The Steam client is quite clearly an x86_32 binary– look at the terminal screenshot above and observe that it’s downloading all :i386 support libraries.

  The file /usr/bin/steam isn’t a binary but a launcher shell script (something you’ll also see if you investigate /usr/bin/firefox on a Linux system). Here’s an interesting tidbit :

  function detect_platform()
  
    # Maybe be smarter someday
    # Right now this is the only platform we have a bootstrap for, so hard-code it.
    echo ubuntu12_32
  
  

  I wager that it’s possible to get Steam running on other distributions, it probably just takes a little more effort (assuming that Steam doesn’t put too much effort into thwarting such attempts).

  As for the FTL game, it comes with binaries and libraries for both x86_32 and x86_64. So, good work to the dev team for creating and testing both versions. FTL also distributes versions of the libraries it expects to work with.

  I suspect that the Steam client overall is largely a WWW rendering engine underneath the covers. That would help explain how Valve is able to achieve such a consistent look and feel, not only across OS platforms, but also through a web browser. When I browse the Steam store through Google Chrome, it looks and feels exactly like the native desktop client. When I first thought of how someone could port Steam to Linux, I immediately wondered about how they would do the UI.

  A little Googling for “steam uses webkit” (just a hunch) confirms my hypothesis.

• Undefined variable : isFileGetContentsInstalled

  23 février 2013, par Grandt

  Undefined variable : isFileGetContentsInstalled
  Rev. 2.10 - 2013-02-23
  
  * Fixed : Undefined variable : isFileGetContentsInstalled