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• avformat_open_input fails only with a custom IO context

  19 janvier 2017, par Tim

  Running into an odd issue with avformat_open_input, it is failing with :

  Invalid data found when processing input

  But this only happens when I attempt to read the file using a custom AVIOContext.

  My custom code is as follows (error checking omitted for clarity) :

  auto fmtCtx = avformat_alloc_context();
  
  auto ioBufferSize = 32768;
  
  auto ioBuffer = (unsigned char *)av_malloc(ioBufferSize);
  
  auto ioCtx = avio_alloc_context(ioBuffer,
  
                                  ioBufferSize,
  
                                  0,
  
                                  reinterpret_cast<void>(this),
  
                                  &amp;imageIORead,
  
                                  NULL,
  
                                  &amp;imageIOSeek));
  
  
  
  fmtCtx -> pb = ioCtx;
  
  fmtCtx -> flags |= AVFMT_FLAG_CUSTOM_IO;
  
  
  
  int err = avformat_open_input(&amp;fmtCtx, NULL, NULL, NULL);
  
  </void>

  imageIOSeek is never called, but properly handles the whence parameter including the AVSEEK_SIZE option. My file data is already loaded in memory, so imageIORead is trivial (returning 0 at EOF) :

  int imageIORead(void *opaque, uint8_t *buf, int buf_size) {
  
      Image *d = (Image *)buf;
  
      int rc = std::min(buf_size, static_cast<int>(d->data.size() - d->pos));
  
  
  
      memcpy(buf, d->data.data() + d->pos, rc);
  
      d->pos += rc;
  
      return rc;
  
  }
  
  </int>

  The data being read is loaded from a file on disk :

  /tmp/25.jpeg

  The following code is able to open and extract the image correctly :

  auto fmtCtx = avformat_alloc_context();
  
  int err = avformat_open_input(&fmtCtx, "/tmp/25.jpeg", NULL, NULL);

  The project is using a minified version of libavformat including only the formats we need. I don’t believe this is the cause of the problem since the file can be open and handled properly when the path is specified. I haven’t seen any configure options specifically targeting support for custom IO contexts.

  This is the image in question : 25.jpeg

• ffserver : local OOB write with custom program name

  6 janvier 2017, par Tobias Stoeckmann

  ffserver : local OOB write with custom program name
  When the command line for children is created, it is assumed that
  
  my_program_name always ends with "ffserver", which doesn’t have to
  
  be true if ffserver is called through a symbolic link.
  In such a case, it could be that not enough space for "ffmpeg" is
  
  available at the end, leading to a buffer overflow.
  One example would be :
  $ ln -s /usr/bin/ffserver /f ; /f
  As this is only a local buffer overflow, i.e. is based on a weird
  
  program call, this has NO security impact.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] ffserver.c

• Design Custom FFmpeg media player in Android for Allwinner A20 device

  22 décembre 2016, par Hardik

  I want to design one custom media player using FFmpeg library in android OS for Allwinner A20 custom board.

  This custom board is having two playback devices HDMI and 3.5mm Jack. So I want to play same audio file to both devices simultaneously.

  I can see device file for both sound card in /dev/snd/pcmC1D0p for HDMI and /dev/snd/pcmC2D0p for 3.5mm Jack. (Note : pcmC0D0p and pcmC0D0p using for some other audio zone)

  I’m using tlv320aic3100 codec with I2s Interface for 3.5mm audio out Jack.

  Using Android media player I’m not able to serve two sound cards simultaneously, So I’m thinking to design custom media player using FFmpeg library.

  I need some predictions and possible challenges in this approach.
  and
  I would be very grateful if somebody could suggest step-wise procedure to do this.