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• FFMpeg API Write AVPackets to new H264 file without Decoding / Transcoding

  15 septembre 2011, par mhathcock

  Using the FFMpeg API in Windows 7 64bit with MSVC++ 2010 :

  Using video files in MP4 container, with Video in H264 and Audio in AAC.

  I can successfullly read packets, decode them, encode them, and write them back to a video file using the normal av_read_frame, avcodec_decode_video, etc.

  What i want to do is read a packet, and write it to the output file immediately, without encoding or decoding. Essentially, to be able to take packets from different video files (that are all identical size, bitrate, fps, etc) and write them into 1 video file.

  I set the packet PTS and DTS to the number of written packets.

  Libx264 does not complain during this process, but the output video file contains no data (headers only ?) and is less than 50kB, and claims a duration of 0.

  Code :

  while( readVal > -1 )
  
  {
  
    readVal = av_read_frame( pFormat, &pkt );
  
  
  
    if ( pkt.stream_index == vidIdx )
  
    {
  
      pkt.pts = packets;
  
      pkt.dts = packets;
  
  
  
      pkt.stream_index = pVideoStream->index;
  
  
  
      av_write_frame( pFmtOut, &pkt );
  
  
  
      printf("Processing packet %i\n", packets );
  
  
  
      ++packets;
  
    } 
  
  }

• ffmpeg reencoding of flv files from MAC

  22 septembre 2011, par Nick Mitin

  I've recorded a video from a webcam on mac and now i'm trying to reencode it, but ffmpeg does not recognize audio stream :

  FFmpeg version git-120610e, Copyright (c) 2000-2010 the FFmpeg developers
    built on Sep 21 2010 15:56:57 with gcc 4.4.1
    configuration : —enable-gpl —enable-version3 —enable-nonfree —enable-postproc —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libtheora —enable-libvorbis —enable-libmp3lame —enable-libx264
    libavutil     50.27. 0 / 50.27. 0
    libavcore      0. 9. 0 /  0. 9. 0
    libavcodec    52.89. 0 / 52.89. 0
    libavformat   52.78. 5 / 52.78. 5
    libavdevice   52. 2. 2 / 52. 2. 2
    libavfilter    1.39. 0 /  1.39. 0
    libswscale     0.11. 0 /  0.11. 0
    libpostproc   51. 2. 0 / 51. 2. 0
  [flv @ 0x1e79470] Estimating duration from bitrate, this may be inaccurate
  Input #0, flv, from '10125174c09241f6536ccbe503ebbc00.flv' :
    Duration : 00:00:22.68, start : 0.000000, bitrate : N/A
      Stream #0.0 : Video : flv, yuv420p, 640x480, 1k tbr, 1k tbn, 1k tbc
      Stream #0.1 : Audio : [0][0][0][0] / 0x0000, 0 channels
  

  Is it possible to make ffmpeg to support audio stream form flv recorded on MAC ?

• What are the specifications of Flex usable FLV videos ?

  26 septembre 2011, par Riduidel

  I have a server which streams FLV files to a Flex client.
  In this flex client, the video timeline advances incoherently, and no video can be seen on screen (only the sound can be heard).

  My FLV file has been generated using ffmpeg, which says (about this generated file)

  FFmpeg version 0.6, Copyright (c) 2000-2010 the FFmpeg developers
  
    built on Aug  8 2010 04:24:04 with gcc 4.3.2
  
    configuration: --prefix=/home/marpada/ffmpegfull --enable-gpl --enable-version3 --enable-nonfree --disable-ffplay --disable-ffserver --enable-libmp3lame --enable-libfaac --enable-libvpx --enable-libfaad --enable-libvorbis --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libxvid --enable-libx264 --enable-libtheora --extra-ldflags=-static --extra-libs='-lvorbis -logg -lxvidcore -lx264 -lopencore-amrnb -lopencore-amrwb -lfaad -lfaac -lvpx -ltheora -lm -lpthread' --enable-small --enable-runtime-cpudetect
  
    libavutil     50.15. 1 / 50.15. 1
  
    libavcodec    52.72. 2 / 52.72. 2
  
    libavformat   52.64. 2 / 52.64. 2
  
    libavdevice   52. 2. 0 / 52. 2. 0
  
    libswscale     0.11. 0 /  0.11. 0
  
  [flv @ 0x95c6aa0]Estimating duration from bitrate, this may be inaccurate
  
  
  
  Seems stream 0 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 25.00 (25/1)
  
  Input #0, flv, from '/appli/perigee_70ri/data/files/ged_bur%0/Imagettes/70ri/279/2/8/20_109021138o.70ri_FLV_preview_.flv':
  
    Metadata:
  
      hasMetadata     : true
  
      hasVideo        : true
  
      hasAudio        : true
  
      duration        : 589
  
      lasttimestamp   : 589
  
      lastkeyframetimestamp: 589
  
      width           : 352
  
      height          : 288
  
      videodatarate   : 199
  
      framerate       : 25
  
      audiodatarate   : 125
  
      audiosamplerate : 44100
  
      audiosamplesize : 16
  
      stereo          : true
  
      filesize        : 25058444
  
      videosize       : 15195503
  
      audiosize       : 9690850
  
      datasize        : 23027
  
      metadatacreator : flvmeta 1.1-r202
  
      audiocodecid    : 2
  
      videocodecid    : 2
  
      audiodelay      : 0
  
      canSeekToEnd    : false
  
      hasCuePoints    : false
  
      hasKeyframes    : true
  
    Duration: 00:09:48.78, start: 0.000000, bitrate: 332 kb/s
  
      Stream #0.0: Video: flv, yuv420p, 352x288, 204 kb/s, 25 tbr, 1k tbn, 1k tbc
  
      Stream #0.1: Audio: mp3, 44100 Hz, 2 channels, s16, 128 kb/s
  
  At least one output file must be specified

  Which, as far as it seems to me, is OK.

  Furthermore, the video plays nice in VLC.