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• ffmpeg - continuous file streaming over RTMP

  1er mai 2013, par Sébastien Renauld

  I've been looking around for a simple (or perhaps not-so-simple) walkaround for a problem I am having in my set up for a simple test case : video streaming over red5 media server.

  I have built a small-ish library of FLV files scraped from YouTube and managed to play them in succession with the following perl script :

  use Cwd;
  
  use strict;
  
  use warnings;
  
  use DBI;
  
  use DBD::mysql;
  
  
  
  our $db = DBI->connect();
  
  my $dst = "/home/seb/youtube/";
  
  sub streamFile {
  
      my $r = $db->prepare("SELECT name FROM music_flvs ORDER BY RAND() LIMIT 1");
  
      $r->execute();
  
      my @data = $r->fetchrow_array();
  
      my $filename = $data[0]
  
      my $t = `ffmpeg -re -i '${dst}${filename}' -ab 48k -ac 1 -vcodec libx264 -crf 30 -s "640x480" -acodec libfaac -ar 44100 -threads 4 -f flv 'rtmp://server/oflaDemo/music'`;
  
      return 1;
  
  }
  
  while (&streamFile()) {
  
  }

  This script does its purpose extremely well : it plays files one by one through ffmpeg. However, it does so with a crucial problem : it causes an Unpublish event every time it swaps songs, which causes all the clients to disconnect. I would like to prevent this. The event manifests itself in ActionScript as this :

   16:33:54:209 - Playback - NetStream.Play.UnpublishNotify
  
   16:33:54:209 - Playback - NetStream.Play.PublishNotify

  I have seen the concat demuxer and believe that it might somewhat help me. The question is pretty simple : what is the best way to make ffmpeg stream a playlist to a RTMP server without ever causing an Unpublish event ?

• FFmpeg : Can't read self-rendered videofile with QTRLE

  10 décembre 2014, par user4240580

  I adjusted the decoding_encoding.c example to use the ARGB pixel format, the QTRLE codec and a live stream.
  I can successfully write my video stream to a file but can’t access the stream again properly.
  I tried something like this :

  if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
  
      exit(1);
  
  }
  
  
  
  /* retrieve stream information */
  
  if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
  
      exit(1);
  
  }
  
  
  
  av_dump_format(fmt_ctx, 0, src_filename, 0);

  similiar to what’s written in the demuxing_decoding.c- and the filtering_video.c-example.

  This results in the program trying to use the AAC-code which obviously fails :

  Initializing ...[aac @ 001d4d60] Format aac detected only with low score of 1, misdetection possible!
  
  [aac @ 001d59a0] channel element 0.0 is not allocated
  
  [aac @ 001d59a0] Reserved bit set.
  
  ...

  Similiarly, I can’t get FFplay to correctly detect the codec ; and when using

  ffplay -formats

  it doesn’t even list qtrle there.

  Do I have to use a mux to properly use qtrle ? I’m confused because the decoding_encoding.c-example doesn’t seem to use any mux but simply sets the codec and everything works ... ?

• lavfi/vf_libvmaf : add warning when color ranges differ

  1er avril 2023, par Chema Gonzalez

  lavfi/vf_libvmaf : add warning when color ranges differ
  The VMAF filter uses the pixel values without considering
  
  the color ranges. This is incorrect. Patch adds a warning
  
  so at least the user knows it.
  Let's see an example.
  (1) Let's get FR and LR versions of the same image.
  ```
  
  $ ffmpeg -y -i /tmp/lena.490x490.ppm -vf scale="out_range=full" -pix_fmt yuv420p /tmp/lena.full.y4m
  
  $ xxd /tmp/lena.full.y4m |head
  
  00000000 : 5955 5634 4d50 4547 3220 5734 3930 2048  YUV4MPEG2 W490 H
  
  00000010 : 3439 3020 4632 353a 3120 4970 2041 303a  490 F25:1 Ip A0 :
  
  00000020 : 3020 4334 3230 6a70 6567 2058 5953 4353  0 C420jpeg XYSCS
  
  00000030 : 533d 3432 304a 5045 4720 5843 4f4c 4f52  S=420JPEG XCOLOR
  
  00000040 : 5241 4e47 453d 4655 4c4c 0a46 5241 4d45  RANGE=FULL.FRAME
  
  00000050 : 0a72 7271 7070 706f 6f6e 6d6d 6c6d 6d6d  .rrqpppoonmmlmmm
  
  00000060 : 6c6e 6e6d 6d6e 6e6e 6d6c 6d6d 6d6d 6d6d  lnnmmnnnmlmmmmmm
  
  00000070 : 6d6e 6d6b 6c6d 6e6e 6d6c 6d6d 6e6e 6f6f  mnmklmnnmlmmnnoo
  
  00000080 : 6f6f 6e6e 6e6e 6f70 7172 7375 7676 7370  oonnnnopqrsuvvsp
  
  00000090 : 6d69 6662 5e59 534d 4845 3d35 302e 2d2c  mifb^YSMHE=50.-,
  
  ```
  ```
  
  $ ffmpeg -y -i /tmp/lena.490x490.ppm -vf scale="out_range=limited" -pix_fmt yuv420p /tmp/lena.limited.y4m
  
  $ xxd /tmp/lena.limited.y4m | head
  
  00000000 : 5955 5634 4d50 4547 3220 5734 3930 2048  YUV4MPEG2 W490 H
  
  00000010 : 3439 3020 4632 353a 3120 4970 2041 303a  490 F25:1 Ip A0 :
  
  00000020 : 3020 4334 3230 6a70 6567 2058 5953 4353  0 C420jpeg XYSCS
  
  00000030 : 533d 3432 304a 5045 4720 5843 4f4c 4f52  S=420JPEG XCOLOR
  
  00000040 : 5241 4e47 453d 4c49 4d49 5445 440a 4652  RANGE=LIMITED.FR
  
  00000050 : 414d 450a 7272 7170 7070 6f6f 6e6e 6e6d  AME.rrqpppoonnnm
  
  00000060 : 6e6e 6e6d 6f6e 6e6e 6e6e 6e6e 6d6e 6e6e  nnnmonnnnnnnmnnn
  
  00000070 : 6e6e 6e6e 6f6e 6c6d 6e6f 6e6e 6d6e 6e6f  nnnnonlmnonnmnno
  
  00000080 : 6f6f 6f6f 6f6f 6f6f 6f6f 7071 7273 7576  oooooooooopqrsuv
  
  00000090 : 7673 706e 6a68 6461 5c57 524e 4b44 3d39  vspnjhda\WRNKD=9
  
  ```
  Note that the 2x images are the same. Only difference is the range,
  
  and the precision issues related to range conversion.
  (2) Let's calculate the VMAF score :
  
  ```
  
  $ ./ffmpeg -filter_threads 1 -filter_complex_threads 1 -i /tmp/lena.full.y4m -i /tmp/lena.limited.y4m -lavfi libvmaf="model=path=/usr/share/model/vmaf_v0.6.1neg.json" -report -f null -
  
  ...
  
  [Parsed_libvmaf_0 @ 0x3cc9b40] VMAF score : 85.530109
  
  ```
  As we are comparing an image with itself, we expect the score to
  
  be close to 100. Issue here is that the VMAF filter just uses the
  
  pixel values, ignoring the color ranges.
  Proposed solution is to add a warning.
  
  ```
  
  $ ./ffmpeg -filter_threads 1 -filter_complex_threads 1 -i /tmp/lena.full.y4m -i /tmp/lena.limited.y4m -lavfi libvmaf="model=path=/us
  
  r/share/model/vmaf_v0.6.1neg.json" -report -f null -
  
  ...
  
  [Parsed_libvmaf_0 @ 0x3cc9b40] distorted and reference frames use different color ranges (pc != tv)
  
  ...
  
  [Parsed_libvmaf_0 @ 0x3cc9b40] VMAF score : 85.530109
  
  ```
  Tested :
  Ran fate.
  
  ```
  
  $ make fate -j
  
  ...
  
  TEST    seek-lavf-ppmpipe
  
  TEST    seek-lavf-pgmpipe
  
  TEST    seek-lavf-mxf_opatom
  
  ```
  

  • [DH] libavfilter/vf_libvmaf.c