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• avformat_open_input fails intermittently with avfoundation due to "audio format is not supported"

  27 septembre 2019, par NaderNader

  My application uses the ffmpeg APIs (avformat, avdevice, etc) to open a selected audio input for encoding. For some inputs I can reliably open them the first time, but when I close and reopen that input later, the avformat_open_input() call fails due to "audio format is not supported". My testing shows that it never fails the first time after starting my, and has only about a 50% chance of success when reopening.

  The failure only occurs with my "Built-in Microphone" audio input. I have a USB audio card that reliably opens and closes repeatedly. I have read the documentation and see that the proper way to free the resources after opening is to call avformat_close_input. The only way I have found to guarantee success is to only open the input once.

  I have written a test program to recreate these failures.

  int main() {
  
  
  
      avdevice_register_all();
  
  
  
      cout << "Running open audio test" << endl;
  
  
  
  
  
      int i;
  
      for(i = 0; i< 10; i++) {
  
  
  
          AVDictionary* options = NULL;
  
          AVInputFormat* inputFormat = av_find_input_format("avfoundation");
  
          if (!inputFormat) {
  
              cout << "avfoundation inputFormat=null" << endl;
  
          }
  
  
  
          AVFormatContext* formatContext = avformat_alloc_context();
  
          int result = avformat_open_input(&formatContext, ":1", inputFormat, &options);
  
          if (result < 0) {
  
              char error[256];
  
              av_strerror(result, error, sizeof(error));
  
              cout << "result=" << result << " " << error << endl;
  
          } else {
  
              cout << "input opened successfully" << endl;
  
          }
  
  
  
          sleep(1);
  
  
  
          avformat_close_input(&formatContext);
  
  
  
          sleep(1);
  
  
  
      }
  
  
  
      return 0;
  
  }

  I would expect the main loop to succeed each time but a typical output shows a high failure rate :

  Running open audio test

  input opened successfully
  
  [avfoundation @ 0x7fdeb281de00] audio format is not supported
  
  result=-5 Input/output error
  
  [avfoundation @ 0x7fdeb2001400] audio format is not supported
  
  result=-5 Input/output error
  
  [avfoundation @ 0x7fdeb2001400] audio format is not supported
  
  result=-5 Input/output error
  
  input opened successfully
  
  input opened successfully
  
  input opened successfully
  
  [avfoundation @ 0x7fdeb2068800] audio format is not supported
  
  result=-5 Input/output error
  
  input opened successfully
  
  input opened successfully

  I have tried increasing the sleep time between close and open to 5 seconds, but saw no difference in behavior.

  The source of the failure is https://github.com/FFmpeg/FFmpeg/blob/master/libavdevice/avfoundation.m#L672

  It appears avfoundation.m internally is opening an input stream and grabbing an audio frame to determine the format, but the value returned is not valid sometimes, when the process has previously opened and closed that input.

  Am I not closing the resources properly ? Do I have a hardware issue specific to my macbook ?

  Additional Details :

  Tested MacBook Pro with MacOS Mojave 10.14.6
  Tested with Ffmpeg 3.4.1, 4.0, and 4.1

  list_devices :

  [AVFoundation input device @ 0x7f80fff066c0] AVFoundation video devices:
  
  [AVFoundation input device @ 0x7f80fff066c0] [0] FaceTime HD Camera
  
  [AVFoundation input device @ 0x7f80fff066c0] [1] Capture screen 0
  
  [AVFoundation input device @ 0x7f80fff066c0] AVFoundation audio devices:
  
  [AVFoundation input device @ 0x7f80fff066c0] [0] Behringer Duplex
  
  [AVFoundation input device @ 0x7f80fff066c0] [1] Built-in Microphone
  
  [AVFoundation input device @ 0x7f80fff066c0] [2] USB Audio CODEC

• avformat_open_input for 24-bit audio fails intermittently with avfoundation due to "audio format is not supported"

  27 septembre 2019, par NaderNader

  My application uses the ffmpeg APIs (avformat, avdevice, etc) to open a selected audio input for encoding. For audio inputs configured for 24-bit I can reliably open them the first time, but when I close and reopen that input later, the avformat_open_input() call fails due to "audio format is not supported". My testing shows that it never fails the first time after starting my, and has only about a 50% chance of success when reopening.

  The failure only occurs when I configure my "Built-in Microphone" audio input for 24-bit integer. 16-bit integer and 32-bit float work reliably. Changing the number of channels and sample rate has no effect.

  I have read the documentation and see that the proper way to free the resources after opening is to call avformat_close_input. The only way I have found to guarantee success is to only open the input once.

  I have written a test program to recreate these failures.

  int main() {
  
  
  
      avdevice_register_all();
  
  
  
      cout << "Running open audio test" << endl;
  
  
  
  
  
      int i;
  
      for(i = 0; i< 10; i++) {
  
  
  
          AVDictionary* options = NULL;
  
          AVInputFormat* inputFormat = av_find_input_format("avfoundation");
  
          if (!inputFormat) {
  
              cout << "avfoundation inputFormat=null" << endl;
  
          }
  
  
  
          AVFormatContext* formatContext = avformat_alloc_context();
  
          int result = avformat_open_input(&formatContext, ":1", inputFormat, &options);
  
          if (result < 0) {
  
              char error[256];
  
              av_strerror(result, error, sizeof(error));
  
              cout << "result=" << result << " " << error << endl;
  
          } else {
  
              cout << "input opened successfully" << endl;
  
          }
  
  
  
          sleep(1);
  
  
  
          avformat_close_input(&formatContext);
  
  
  
          sleep(1);
  
  
  
      }
  
  
  
      return 0;
  
  }

  I would expect the main loop to succeed each time but a typical output shows a high failure rate :

  Running open audio test

  input opened successfully
  
  [avfoundation @ 0x7fdeb281de00] audio format is not supported
  
  result=-5 Input/output error
  
  [avfoundation @ 0x7fdeb2001400] audio format is not supported
  
  result=-5 Input/output error
  
  [avfoundation @ 0x7fdeb2001400] audio format is not supported
  
  result=-5 Input/output error
  
  input opened successfully
  
  input opened successfully
  
  input opened successfully
  
  [avfoundation @ 0x7fdeb2068800] audio format is not supported
  
  result=-5 Input/output error
  
  input opened successfully
  
  input opened successfully

  I have tried increasing the sleep time between close and open to 5 seconds, but saw no difference in behavior. While this program runs, I can use the MacOS Audio MIDI Setup to change the microphone input configuration and watch the output change from all success to intermittent errors.

  The source of the failure is https://github.com/FFmpeg/FFmpeg/blob/master/libavdevice/avfoundation.m#L672

  It appears avfoundation.m internally is opening an input stream and grabbing an audio frame to determine the format, but the value returned is not valid sometimes, when the process has previously opened and closed that input.

  Am I not closing the resources properly ? Do I have a hardware issue specific to my macbook ?

  Additional Details :

  Tested MacBook Pro with MacOS Mojave 10.14.6
  Tested with Ffmpeg 3.4.1, 4.0, and 4.1

  list_devices :

  [AVFoundation input device @ 0x7f80fff066c0] AVFoundation video devices:
  
  [AVFoundation input device @ 0x7f80fff066c0] [0] FaceTime HD Camera
  
  [AVFoundation input device @ 0x7f80fff066c0] [1] Capture screen 0
  
  [AVFoundation input device @ 0x7f80fff066c0] AVFoundation audio devices:
  
  [AVFoundation input device @ 0x7f80fff066c0] [0] Behringer Duplex
  
  [AVFoundation input device @ 0x7f80fff066c0] [1] Built-in Microphone
  
  [AVFoundation input device @ 0x7f80fff066c0] [2] USB Audio CODEC

• avformat/matroskadec : Fix use-after-free when demuxing ProRes

  7 décembre 2019, par Andreas Rheinhardt

  avformat/matroskadec : Fix use-after-free when demuxing ProRes
  ProRes in Matroska is supposed to not contain the first atom header
  
  (containing a size field and the tag "icpf") and therefore the Matroska
  
  demuxer has to recreate it ; this involves an allocation and copy, of
  
  course. Whether the old buffer (containing the data without the atom
  
  header) needs to be freed or not depends upon whether it is what was
  
  directly read (in which case it is owned by an AVBuffer) or whether it
  
  has been allocated when reversing the track's content compression (e.g.
  
  zlib compression) that Matroska supports.
  So there are three pointers involved : The one pointing to the directly
  
  read data (owned by the AVBuffer), the one pointing to the currently
  
  valid data (which coincides with the former if no content compression
  
  needed to be reverted) and the one pointing to the new data with the
  
  first atom header. The check for whether to free the second of these is
  
  simply whether the first two are different.
  This works mostly, but there is a complication : Some muxers don't strip
  
  the first atom header away and in this case, it is also not reinserted
  
  and no new buffer is allocated ; instead, the second and the third
  
  pointers agree. In this case, one must never free the second buffer.
  
  Yet it is currently done if the track is e.g. zlib compressed.
  
  This commit fixes this.
  This is a regression since b8e75a2a.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavformat/matroskadec.c