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• Decoder return of av_find_best_stream vs. avcodec_find_decoder

  7 octobre 2016, par Jason C

  The docs for libav’s av_find_best_stream function (libav 11.7, Windows, i686, GPL) specify a parameter that can be used to receive a pointer to an appropriate AVCodec :

  decoder_ret - if non-NULL, returns the decoder for the selected stream

  There is also the avcodec_find_decoder function which can find an AVCodec given an ID.

  However, the official demuxing + decoding example uses av_find_best_stream to find a stream, but chooses to use avcodec_find_decoder to find the codec in lieu of av_find_best_stream’s codec return parameter :

  ret = av_find_best_stream(fmt_ctx, type, -1, -1, NULL, 0);
  
  ...
  
  stream_index = ret;
  
  st = fmt_ctx->streams[stream_index];
  
  ...
  
  /* find decoder for the stream */
  
  dec = avcodec_find_decoder(st->codecpar->codec_id);

  As opposed to something like :

  ret = av_find_best_stream(fmt_ctx, type, -1, -1, &dec, 0);

  My question is pretty straightforward : Is there a difference between using av_find_best_stream’s return parameter vs. using avcodec_find_decoder to find the AVCodec ?

  The reason I ask is because the example chose to use avcodec_find_decoder rather than the seemingly more convenient return parameter, and I can’t tell if the example did that for a specific reason or not. The documentation itself is a little spotty and disjoint, so it’s hard to tell if things like this are done for a specific important reason or not. I can’t tell if the example is implying that it "should" be done that way, or if the example author did it for some more arbitrary personal reason.

• FFMPEG install on server

  23 juillet 2013, par s19k15

  I have an online server (shared hosting plan) in linux, i do not know a lot stuff about linux and i am trying to install ffmpeg.

  I have tryied a lot of scripts but no luck.
  Now i am trying to install the below script via putty.
  <a href="https://github.com/heidisoft/FFMPEG-install-script-for-shared-host" rel="nofollow">https://github.com/heidisoft/FFMPEG-install-script-for-shared-host</a>

  When the install was running i get this message and the installation stops...

  Installation of MPlayer-1.0rc1.tar.bz2 ....... started
  
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
  
                                   Dload  Upload   Total   Spent    Left  Speed
  
  100  1233  100  1233    0     0   7713      0 --:--:-- --:--:-- --:--:--  7803
  
  bzip2: (stdin) is not a bzip2 file.
  
  tar: Child returned status 2
  
  tar: Error is not recoverable: exiting now
  
  mplayer.sh: line 32: cd: MPlayer-1.0rc1/: No such file or directory
  
  mplayer.sh: line 33: ./configure: No such file or directory
  
  make: *** No targets specified and no makefile found.  Stop.
  
  make: *** No rule to make target `install'.  Stop.
  
  cp: cannot stat `etc/codecs.conf': No such file or directory
  
  Installation of MPlayer-1.0rc1.tar.bz2 ....... Completed
  
  
  
          Mplayer installation Failed :( , please visit the forum

  What can i do to install ??? Thanks !

• ffmpeg errors in the daemon

  3 octobre 2020, par smoto_shei

  I created a shell script to compress a video using ffmpeg(4.3.1).

  


  ffmpeg -y -i \
 '/var/www/System/Backend/Outputs/TempSaveMovie/200703_4_short_5fr_p2(100_20)_r(50_20).mp4' \
 -vcodec h264 -an \
 '/var/www/System/Backend/Outputs/MovieOutputs/200703_4_short_5fr_p2(100_20)_r(50_20).mp4'



  


  If you run this code from the console, it will run without problems.
In fact, we're using the python subscript.call() to execute it. It works fine too.

  


  cmd = 'sh /var/www/System/Backend/cv2toffmpeg.sh'
subprocess.call(cmd, shell=True)


  


  Secondly, if I run it from a daemonized python program, I'll get an error. I get the following error.
You'll get an error like this

  


  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from './Outputs/TempSaveMovie/200703_4_short_5fr_p2(100_20)_r(50_20).mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf58.35.100
  Duration: 00:00:06.15, start: 0.000000, bitrate: 10246 kb/s
    Stream #0:0(und): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 10244 kb/s, 13 fps, 13 tbr, 13312 tbn, 13 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg4 (native) -> h264 (h264_nvenc))
Press [q] to stop, [?] for help
[mpeg4 @ 0x55cec17c5480] header damaged
[mpeg4 @ 0x55cec17c6840] header damaged
[mpeg4 @ 0x55cec1855f80] header damaged
[mpeg4 @ 0x55cec1866e00] header damaged
Output #0, mp4, to './Outputs/MovieOutputs/200703_4_short_5fr_p2(100_20)_r(50_20).mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf58.45.100
    Stream #0:0(und): Video: h264 (h264_nvenc) (Main) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 2000 kb/s, 13 fps, 13312 tbn, 13 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc58.91.100 h264_nvenc
    Side data:
      cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 4000000 vbv_delay: N/A
Error while decoding stream #0:0: Invalid data found when processing input
[mpeg4 @ 0x55cec17c8780] header damaged
Error while decoding stream #0:0: Invalid data found when processing input
[mpeg4 @ 0x55cec17c5480] header damaged


  


  I think the problem is when you run it from a daemonized process. There seems to be a similar problem in the past.
Ffmpeg does not properly convert videos when run as daemon
I would like to ask for your help to solve this problem. Thank you for your help from Japan.