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• What happens if I ffmpeg encode two times successively with the same bitrate

  3 juin 2019, par a a

  I have a original divx video (3500k) which I encode to h.264 in a mp4 container. I choose to encode it with 1000 k for instance so that the quality stays close to the original. What happens if I encode it then one more time with the same bitrate ? Theoretically should the quality stay the same ?

  ffmpeg -i A.divx -an -vcodec h264  -b:v 100k A.mp4

• FFMPEG stops converting

  19 février 2014, par user3328745

  I've got Ubuntu 12.04 LTS, which runs Wowza Media Server, so I use FFmpeg as a transcoder for live streaming and JWplayer on my website. But ffmpeg always stops converting, and I have to input the command again and again. So here is the command :

  nohup ffmpeg -i rtsp://log:pass@<cameraip>:554/live1.sdp -ar 44100 -ab 128k -f flv -b 5000k -s 480x270 -y rtmp://<serverip>:1935/live/camera.stream &amp;
  
  </serverip></cameraip>

  And that's what i get

  ffmpeg version 0.8.10-4:0.8.10-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  
    built on Feb  6 2014 20:56:59 with gcc 4.6.3
  
  *** THIS PROGRAM IS DEPRECATED ***
  
  This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
  
  [rtsp @ 0x25317a0] Estimating duration from bitrate, this may be inaccurate
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 150.00 (150/1) -> 1000.00 (1000/1)
  
  Input #0, rtsp, from &#39;rtsp://log:pass@<cameraip>:554/live1.sdp&#39;:
  
    Metadata:
  
      title           : RTSP/RTP stream 1 from DCS-2132L
  
      comment         : live1.sdp with v2.0
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: h264 (High), yuvj420p, 640x360 [PAR 1:1 DAR 16:9], 75 fps, 1k tbr, 90k tbn, 150 tbc
  
      Stream #0.1: Audio: pcm_mulaw, 8000 Hz, 1 channels, s16, 64 kb/s
  
  Incompatible pixel format &#39;yuvj420p&#39; for codec &#39;mpeg4&#39;, auto-selecting format &#39;yuv420p&#39;
  
  [buffer @ 0x2539f80] w:640 h:360 pixfmt:yuvj420p
  
  [scale @ 0x253a940] w:640 h:360 fmt:yuvj420p -> w:480 h:270 fmt:yuv420p flags:0x4
  
  Incompatible sample format &#39;s16&#39; for codec &#39;ac3&#39;, auto-selecting format &#39;flt&#39;
  
  [ac3 @ 0x2531120] channel_layout not specified
  
  [ac3 @ 0x2531120] No channel layout specified. The encoder will guess the layout, but it might be incorrect.
  
  [ac3 @ 0x2531120] invalid bit rate
  
  Output #0, avi, to &#39;rtmp://<serverip>:1935/live/camera.stream&#39;:
  
      Stream #0.0: Video: mpeg4, yuv420p, 480x270 [PAR 1:1 DAR 16:9], q=2-31, 1024 kb/s, 90k tbn, 1k tbc
  
      Stream #0.1: Audio: ac3, 22050 Hz, mono, flt, 1024 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
  Error while opening encoder for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height
  
  </serverip></cameraip>

  Plese, help me to correct the errors

• HTTP Header for Duration of a MP4 for HTML 5 video

  9 mars 2014, par Mustafa

  I am trying to stream MP4 video as it is encoded from a webserver. I believe I used the appropriate flags, but it is not working correctly. When I download the video from my stream and open it with VLC, it properly shows the duration. Since a socket is not seekable, I assume it writes the metadata to end ? My Chrome browser always shows 8 seconds duration. The first 8 seconds plays at the normal speed, but afterwards the pause button turns into play button and the video plays very fast, probably as fast as it is recieved. However the audio is played at normal speed. I tried document.getElementById('myVid').duration = 20000 but it is a readonly field.

  I wonder, is there anyway to explicitly state the duration in HTTP headers or in any other way ? I cannot find any documentation about it.

  ffmpeg -i - -vcodec libx264 -acodec libvo_aacenc -ar 44100 -ac 2 -ab 128000 -f mp4 -movflags frag_keyframe+faststart pipe:1 -fflags +genpts -re -profile baseline -level 30 -preset fast

  To close-voters, that thinks it is not programming related, I use it in my own server I coded, and I need to set the duration programatically via JavaScript or setting the HTTP header. I believe it may be related to both ffmpeg or http headers, that's why I posted it here.

  app.get("/video/*", function(req,res){
  
      res.writeHead(200, {
  
          'Content-Type': 'video/mp4',
  
      });
  
      var dir = req.url.split("/").splice(2).join("/");
  
      var buf = new Buffer(dir, 'base64');
  
      var src = buf.toString();
  
  
  
      var Transcoder = require('stream-transcoder');
  
      var stream = fs.createReadStream(src);
  
      // I added my own flags to this module, they are at below:
  
      new Transcoder(stream)
  
          .videoCodec('libx264')
  
          .audioCodec("libvo_aacenc")
  
          .sampleRate(44100)
  
          .channels(2)
  
          .audioBitrate(128 * 1000)
  
          .format('mp4')
  
          .on('finish', function() {
  
              console.log("finished");
  
          })
  
          .stream().pipe(res);
  
  });

  exec function in that stream-transcoder module,

      a.push("-fflags");
  
      a.push("+genpts");
  
      a.push("-re");
  
      a.push("-profile");
  
      a.push("baseline");
  
      a.push("-level");
  
      a.push("30");
  
      a.push("-preset");
  
      a.push("fast");
  
      a.push("-strict");
  
      a.push("experimental");
  
      a.push("-frag_duration");
  
      a.push("" + 2 * (1000 * 1000));
  
      var child = spawn('ffmpeg', a, {
  
          cwd: os.tmpdir()
  
      });