Recherche avancée

Sur d’autres sites (10325)

• Input transparent motions into FFMPEG pipe:0

  29 septembre 2021, par NTPHCM

  I follow this to bring a stdinput to FFMPEG.

  


  The idea is : we use AS3 to capture every frame in Animate to byteArray (with ARGB pixel format - means the frame can have transparancy background). After that, we transfer that byteArray to FFMPEG to get output.

  


  If I capture non-transparency picture (the picture with background), the process works well to create motion video.

  


  But when I capture transparency picture and make motion (multi-frame video), the problem appears as below :
Output picture

  


  We can see the bird print a long streak, but I expect one bird flying from the right to the left like this.

  


  It seems like the previous frames are not cleared. Do you have any suggestions to solve this ?

  


• Output video to both file and pipe : simultaneously using FFmpeg Libav

  27 mai 2022, par Hillel Rosensweig

  I have been trying to output video (from my webcam) simultaneously to both a file ('out.mkv') and pipe :
The file gets filtered frames, and the pipe : gets unfiltered rawvideo.
My frame rate is 30 fps. However, I am getting a far lower framerate in my file output.

  


  Attached is the while loop which reads packets and writes them to output :

  


  while (1) {
    av_read_frame(ifmt_ctx, packet);
    stream_index = packet->stream_index;
    StreamContext *stream = &file_stream_ctx[stream_index];
    av_packet_rescale_ts(packet,
                     ifmt_ctx->streams[stream_index]->time_base,
                     stream->dec_ctx->time_base);
    avcodec_send_packet(stream->dec_ctx, packet);

    while (ret >= 0) {
        avcodec_receive_frame(stream->dec_ctx, stream->dec_frame);
        stream->dec_frame->pts = stream->dec_frame->best_effort_timestamp;
        ret = filter_encode_write_frame(stream->dec_frame, stream_index,file_stream_ctx,file_filter_ctx, file_ofmt_ctx);
        ret = av_interleaved_write_frame(pipe_ofmt_ctx, packet);
    }
}


  


  'ifmt_ctx' is the AVFormatContext for the webcam.
'file_ofmt_ctx', is the AVFormatContext for the pipe for the output file, and pipe_ofmt_ctx is the AVFormatContext.
'file_stream_ctx' and 'file_filter_ctx' are the stream and filter contexts used for filtering and encoding the file output.

  


  My guess is that writing to the pipe is taking too long and not allowing the next packet to be read on time - causing a lower frame rate. Does that make sense ? If so - any suggestions on how to fix it ? (I tried using AVFMT_FLAG_NONBLOCK but it doesn't seem to help).

  


  Thanks
Hillel

  


• Receiving multiple files from ffmpeg via subprocesses.PIPE

  11 avril 2022, par Per Plexi

  I am using ffmpeg to convert a video into images. These images are then processed by my Python program. Originally I used ffmpeg to first save the images to disk, then reading them one by one with Python.

  



  This works fine, but in an effort to speed up the program I am trying to skip the storage step and only work with the images in memory.

  



  I use the following ffmpeg and Python subproccesses command to pipe the output from ffmpeg to Python :

  



  command = "ffmpeg.exe -i ADD\\sg1-original.mp4 -r 1 -f image2pipe pipe:1"
pipe = subprocess.Popen(ffmpeg-command, stdout = subprocess.PIPE, stderr = subprocess.PIPE)
image = Image.new(pipe.communicate()[0])


  



  The image variable can then be used by my program. The problem is that if I send more than 1 image from ffmpeg all the data is stored in this variable. I need a way to separate the images. The only way I can think of is splitting on jpeg markers end of file (0xff, 0xd9). This works, but is unreliable.

  



  What have I missed regarding piping files with subproccesses. Is there a way to only read one file at a time from the pipeline ?