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• Revision 6498516bb6 : Change eob[] array type in splitmv RD loop to a regular integer. Change-Id : I24

  23 octobre 2012, par Ronald S. Bultje

  Changed Paths : Modify /vp8/encoder/rdopt.c Change eob[] array type in splitmv RD loop to a regular integer. Change-Id : I240d6b50069fd3f35cc4fed2f4507796f0ef25e9

• Python : Strange hanging behavior when piping large stdout of a subprocess

  7 septembre 2017, par Victor Odouard

  I am currently calling ffmpeg to extract a binary data stream from a video file, and then putting that binary data into a list. There is a lot of data in this data stream, about 4,000 kb. Here is the code

  # write and call ffmpeg command, piping stdout
  
  cmd = "ffmpeg -i video.mpg -map 0:1 -c copy -f data -"
  
  proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
  
  
  
  # read from stdout, byte by byte
  
  li = []
  
  for char in iter(lambda: proc.stdout.read(1), ""):
  
      li.append(char)

  This works fine. However, if I take out the part where I am reading from stdout, it starts working but then hangs :

  cmd = "ffmpeg -i video.mpg -map 0:1 -c copy -f data -"
  
  proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
  
  time.sleep(10)

  I had to add time.sleep(10) at the end or else the process would end before the subprocess, causing this error :

  av_interleaved_write_frame(): Invalid argument
  
  Error writing trailer of pipe:: Invalid argument
  
  size=       0kB time=00:00:00.00 bitrate=N/A speed=N/A
  
  video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing ove
  
  rhead: 0.000000%
  
  Conversion failed!

  Calling either subprocess.call(cmd, stdout=subprocess.PIPE) or subprocess.call(cmd) also cause hanging (the latter just displays the stdout in the console while the former doesn’t).

  Is there something about reading from stdout that prevents this hanging (like perhaps the buffer getting cleared), or am I unknowingly introducing a bug elsewhere ? I’m worried that such a small change causes the program to break ; it doesn’t inspire very much confidence.

  The other issue with this code is that I need to read from the list from another thread. This might mean I need to use a Queue. But when I execute the below code, it takes 11 seconds as opposed to 3 seconds with the list equivalent :

  cmd = "ffmpeg -i video.mpg -loglevel panic -hide_banner -map 0:1 -c copy -f data -"
  
  proc = subprocess.Popen(cmd, stdout=subprocess.PIPE)
  
  
  
  q = Queue()
  
  
  
  for char in iter(lambda: proc.stdout.read(1), ""):
  
      q.put(char)

  Should I be using another data structure ?

• avcodec_encode_video returns 0 as output size

  11 juin 2014, par vacetahanna

  Hello what I am doing wrong ? When I try to encode a Frame, the out_size is 0. and if I use the avcodec_encode_video2 the return value is 0, which indicates, that everything went good, but the avpkt.size is 0 after that. What am I missing or doing wrong ? thank you so much here is my code

  int EncodeVideoFFMPEG::enc_main( void *istream, void *outstream, int width, int height )
  
  {
  
  
  
  avcodec_register_all();
  
  //choose codec
  
  AVCodec *codec = avcodec_find_encoder(CODEC_ID_H264);
  
  
  
  //set parameters
  
  AVCodecContext *c = avcodec_alloc_context3(codec);
  
  c->codec_type = AVMEDIA_TYPE_VIDEO;
  
  c->bit_rate = 50000;
  
  c->pix_fmt = PIX_FMT_YUV420P;
  
  c->width = width;
  
  c->height = height;
  
  c->time_base.num = 1;
  
  c->time_base.den = 25;
  
  c->gop_size = 20;
  
  c->max_b_frames = 0;
  
  
  
  //open
  
  avcodec_open2(c, codec, NULL);
  
  
  
  int got_packet;
  
  
  
  int BYTEPIC = width * height * 3;
  
  
  
  //prepare for changing color space
  
  struct SwsContext *img_convert_ctx1 =
  
  sws_getContext(width, height, PIX_FMT_BGR24,
  
  width, height, PIX_FMT_YUV420P,
  
  SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  //allocateframesforcolorspacechange
  
  AVFrame *pictureBGR = alloc_pictureBGR24(width, height);
  
  AVFrame *picture = alloc_picture420P(width, height);
  
  
  
  //get frame from OGRE and let pictureBGR point to it
  
  unsigned char *image = new unsigned char[BYTEPIC];
  
  memcpy(image, istream, BYTEPIC);
  
  
  
  //change from BGR to 420P
  
  sws_scale(img_convert_ctx1, &image, pictureBGR->linesize, 0, height, picture->data, picture->linesize);
  
  
  
  delete image;
  
  
  
  AVPacket avpkt;
  
  av_new_packet( &avpkt, BYTEPIC );
  
  
  
  //encode withthe codec
  
  int out_size = avcodec_encode_video(c, avpkt.data, avpkt.size, picture);
  
  //int success = avcodec_encode_video2(c, &avpkt, picture, &got_packet);  
  
  
  
  outstream = avpkt.data;
  
  
  
  return out_size;
  
  
  
      }