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• avcodec/h264dec : Fix data race when updating decode_error_flags

  12 septembre 2023, par Andreas Rheinhardt

  avcodec/h264dec : Fix data race when updating decode_error_flags
  When using multi-threaded decoding, every decoding thread
  
  has its own DBP consisting of H264Pictures and each of these
  
  points to its own AVFrames. They are synced during
  
  update_thread_context via av_frame_ref() and therefore
  
  the threads actually decoding (as well as all the others)
  
  must not modify any field that is copied by av_frame_ref()
  
  after ff_thread_finish_setup().
  Yet this is exactly what happens when an error occurs
  
  during decoding and the AVFrame's decode_error_flags are updated.
  
  Given that these errors only become apparent during decoding,
  
  this can't be set before ff_thread_finish_setup() without
  
  defeating the point of frame-threading ; in practice,
  
  this meant that the decoder did not set these flags correctly
  
  in case frame-threading was in use. (This means that e.g.
  
  the ffmpeg cli tool fails to output its "corrupt decoded frame"
  
  message in a nondeterministic fashion.)
  This commit fixes this by adding a new H264Picture field
  
  that is actually propagated across threads ; the field
  
  is an AVBufferRef* whose data is an atomic_int ; it is
  
  atomic in order to allow multiple threads to update it
  
  concurrently and not to provide synchronization
  
  between the threads setting the field and the thread
  
  ultimately returning the AVFrame.
  This unfortunately has the overhead of one allocation
  
  per H264Picture (both the original one as well as
  
  creating a reference to an existing one), even in case
  
  of no errors. In order to mitigate this, an AVBufferPool
  
  has been used and only if frame-threading is actually
  
  in use. This expense will be removed as soon as
  
  a proper API for refcounted objects (not based upon
  
  AVBuffer) is in place.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/h264_picture.c
  • [DH] libavcodec/h264_slice.c
  • [DH] libavcodec/h264dec.c
  • [DH] libavcodec/h264dec.h

• ffmpeg generates "unconnected output" error using -filte_complext [closed]

  25 juillet 2023, par ConiferRod

  I'm trying to combine the rtsp streams of 4 Wyze cameras into a single stream and pipe the result into ffplay (Windows 11). My -filter_complex generates an 'unconnected output' error.

  


  The command :
"C :\Program Files\ffmpeg\ffmpeg.exe" ^
-i rtsp ://user:password@10.0.0.239/live ^
-i rtsp ://user:password@10.0.0.181/live ^
-i rtsp ://user:password@10.0.0.251/live ^
-i rtsp ://user:password@10.0.0.252/live ^
-filter_complex "[0:v][1:v][2:v][3:v]xstack=inputs=4:layout=0_0|w0_0|0_h0|w0_h0[v]" -map '[v]' ^
| "C :\Program Files\ffmpeg\ffplay.exe" -

  


  The error :
[fc#0 @ 000001f45c979d40] Filter xstack:default has an unconnected output
Error : Invalid argument
fd: : Invalid data found when processing input 0KB sq= 0B f=0/0

  


• Handling "NullReferenceException" when executing "ffmpeg.exe" process in C# [duplicate]

  1er juillet 2023, par FrostDream

  I'm trying to execute the "ffmpeg.exe" process in my C# application to process media files. However, I'm encountering a "NullReferenceException" when running the code. I've tried various approaches, including using a try-catch block, but the exception still persists. Here's the relevant code snippet :

  


  bool isValidMedia = true;

try
{
    Process process = new Process();
    process.StartInfo.FileName = "ffmpeg.exe";
    process.StartInfo.Arguments = $"-i \"{file}\" -f null -";
    process.StartInfo.UseShellExecute = false;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.CreateNoWindow = true;
    process.OutputDataReceived += (sender, e) =>
    {
        if (!string.IsNullOrEmpty(e.Data))
        {
            int startIndex = e.Data.IndexOf("samples=") + 8;
            button.Width = int.Parse(e.Data.Substring(startIndex, e.Data.IndexOf(" ") - startIndex)) / zoom * 100;
        }
        else
        {
            isValidMedia = false;
        }
    };

    process.Start();
    process.BeginOutputReadLine();
    process.WaitForExit();
}
catch
{
    isValidMedia = false;
}

if (!isValidMedia)
{
    MessageBox.Show("Not a valid media.");
    return;
}



  


  I suspect that the issue may be related to the asynchronous execution of the event handler or the initialization of the ProcessStartInfo object. Can anyone please help me identify the cause of the "NullReferenceException" and provide guidance on how to resolve it ? Thank you in advance for your assistance.