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• FFMPEG : Redirecting Matroska muxed data to socket

  14 août 2016, par Parth Shah

  I am using FFMPEG library to mux H.264 and AAC frames to Matroska (.mkv) file. I can do that both using command line and C program.

  Now, instead of writing the muxed matroska data in to file I want to write these muxed data directly on to socket or pipe. My actual goal is to write a C program that send muxed data to socket and server will receive this muxed data.

  I tried using protocol tcp. They are working with the matroska format.
  So, My C program is able to send muxed data successfully over socket and server is able to receive this muxed data.

  But when I apply ffprobe command over the received file, I am getting duration and bitrate field N/A. and when I tried to play this file with vlc i am unable to seek the file and getting garbage duration.

  Below the output of the ffprobe.

  ffprobe version N-65784-g50a35f0 Copyright (c) 2007-2014 the FFmpeg developers
  
    built on Aug 25 2014 12:31:36 with gcc 4.7 (Ubuntu/Linaro 4.7.3-1ubuntu1)
  
    configuration: 
  
    libavutil      54.  5.100 / 54.  5.100
  
    libavcodec     56.  0.101 / 56.  0.101
  
    libavformat    56.  1.100 / 56.  1.100
  
    libavdevice    56.  0.100 / 56.  0.100
  
    libavfilter     5.  0.101 /  5.  0.101
  
    libswscale      3.  0.100 /  3.  0.100
  
    libswresample   1.  1.100 /  1.  1.100
  
  Input #0, matroska,webm, from 'Array.mkv':
  
    Metadata:
  
      ENCODER         : Lavf54.29.104
  
    Duration: N/A, start: 1412858260.281000, bitrate: N/A
  
      Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg), 2000x1496 [SAR 1:1 DAR 250:187], 27 fps, 27 tbr, 1k tbn, 1k tbc (default)
  
      Stream #0:1: Video: mjpeg, yuvj422p(pc, bt470bg), 2000x1496 [SAR 1:1 DAR 250:187], 27 fps, 27 tbr, 1k tbn, 1k tbc (default)
  
      Stream #0:2: Video: mjpeg, yuvj422p(pc, bt470bg), 2000x1496 [SAR 1:1 DAR 250:187], 27 fps, 27 tbr, 1k tbn, 1k tbc (default)
  
      Stream #0:3: Video: mjpeg, yuvj422p(pc, bt470bg), 2000x1496 [SAR 1:1 DAR 250:187], 27 fps, 27 tbr, 1k tbn, 1k tbc (default)

  As You can see Duration and Bitrate field shows N/A. However I am getting correct startTime.

  Any help or advice ? Thank you in advance.

• YouTube's HD Video Streaming Server Technology ?

  30 septembre 2013, par bgentry

  Lately I've been researching different methods for streaming MP4s to the browser. Flash Media Server is an obvious choice here (using Cloudfront), and most solutions I've seen use the RTMP protocol.

  However, I spent some time on YouTube with Firebug and Chrome debugger figuring out how their streaming worked and I discovered some interesting differences between some of their videos and quality rates.

  My two sample videos are A and B. A is available up to 480p and B is available up to 1080p. For both videos, all rates up to 480p are served in an FLV container with H.264 video and AAC audio, over HTTP. What's interesting here is that if you have not yet downloaded (cached) the entire video, and you try to skip forward to an uncached part of the video, a new request will be made with a 'begin' parameter equal to the target offset in milliseconds. Example from Video A at 480p :

  http://v11.lscache8.c.youtube.com/videoplayback?ip=0.0.0.0&sparams=id%2Cexpire%2Cip%2Cipbits%2Citag%2Calgorithm%2Cburst%2Cfactor%2Coc%3AU0dWTldQVF9FSkNNNl9PSlhJ&fexp=904806%2C902906%2C903711&algorithm=throttle-factor&itag=35&ipbits=0&burst=40&sver=3&expire=1279756800&key=yt1&signature=D2D704D63C242CF187CAA5B5D5BAFB8DFACAC5FF.39180C01559C976717B651A7EB1D0C6249231EB7&factor=1.25&id=8568eb3135971f6f&begin=111863
  
  
  
  Response Headers:
  
  Cache-Control:public,max-age=23472
  
  Connection:close
  
  Content-Length:14320637
  
  Content-Type:video/x-flv
  
  Date:Wed, 21 Jul 2010 17:23:48 GMT
  
  Expires:Wed, 21 Jul 2010 23:55:00 GMT
  
  Last-Modified:Wed, 19 May 2010 12:31:41 GMT
  
  Server:gvs 1.0
  
  X-Content-Type-Options:nosniff

  The file returned by this URL is a fully valid FLV containing only the portion of the video after the requested offset.

  I did the same kind of test on the higher resolution versions of Video B. At 720p and 1080p, YouTube will return a video in an MP4 container, also with H.264 video and AAC audio. What's impressive to me is that their server takes the same type of offset for an MP4 video (via the 'begin' parameter) and returns a valid, streamable MP4 (moov atom at the front of the file with correct offsets) that also only includes the requested portion of the video.

  So, how does YouTube do this ? How do they generate the FLV or MP4 container on the fly with the correct headers and only the desired segment of the requested video ? I know this can be accomplished using FFMPEG to seek to the desired start point and the qt-faststart script to reposition the moov atom to the front of the stream, but it seems like this would be too slow to handle on-demand for millions of YouTube viewers.

  Ideas ?

  Thanks in advance !

  Footnote : I am not allowed to include more than 1 link at this point, so here is Video A's URL : http:// www.youtube .com/watch ?v=hWjrMTWXH28 "Video available up to 480p"

• How to hack ffmpeg to consider I-Frames as key frames ?

  2 février 2012, par justanothercoder

  I'm trying to get ffmpeg to seek h264 interlaced videos, and i found that i can seek to any frame if i just force it.

  I already hacked the decoder to consider I - Frames as keyframes, and it works nicely with the videos i need it to work with. And there will NEVER be any videos encoded with different encoders.

  However, i'd like the seek to find me an I - Frame and not just any frame.

  What i'd need to do is to hack The AVIndexEntry creation so that it marks any frame that is an I-Frame to be a key frame.
  Or alternatively, hack the search thing to return I - Frames.

  The code does get a tad dfficult to follow at this point.

  Can someone please point me at the correct place in ffmpeg code which handles this ?