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• ffmpeg av_seek_frame

  27 août 2015, par Jack Edmonds

  I am attempting to seek in a movie using ffmpeg’s av_seek_frame method however I’m having the most trouble determining how to generate a time-stamp to seek to. Assuming I want to seek x amount of frames either forward or backward and I know what frame the movie is currently on, how would I go about doing this ?

• ffmpeg : convert audio-only flv to swf

  5 octobre 2011, par Michael Brewer-Davis

  My Flex application records audio-only FLV files using red5—I'd like to convert these to SWF files so I can embed them in other SWF files. (I could also convert to MP3 and then embed them into SWFs myself, but I'd prefer a one step solution.)

  Anyone have experience doing this ?

  What I've tried :

  The following naive ffmpeg command fails :

  > ffmpeg -i 3139747641.flv -vn movie.swf
  
  FFmpeg version SVN-r21751-snapshot, Copyright (c) 2000-2010 Fabrice Bellard, et al.
  
    built on Feb 11 2010 09:15:42 with gcc 4.2.1 (SUSE Linux)
  
    configuration: --enable-gpl --enable-nonfree
  
    libavutil     50. 9. 0 / 50. 9. 0
  
    libavcodec    52.53. 0 / 52.53. 0
  
    libavformat   52.52. 0 / 52.52. 0
  
    libavdevice   52. 2. 0 / 52. 2. 0
  
    libswscale     0.10. 0 /  0.10. 0
  
  [flv @ 0x8a5e3a0]Could not find codec parameters (Video: 0x0000)
  
  [flv @ 0x8a5e3a0]Estimating duration from bitrate, this may be inaccurate
  
  Input #0, flv, from '3139747641.flv':
  
    Metadata:
  
      audiocodecid    : -1
  
      duration        : 0
  
      videocodecid    : -1
  
      canSeekToEnd    : true
  
    Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
  
      Stream #0.1: Audio: nellymoser, 8000 Hz, mono, s16
  
  Output #0, swf, to 'movie.swf':
  
      Stream #0.0: Audio: 0x0000, 8000 Hz, mono, s16, 64 kb/s
  
  Stream mapping:
  
    Stream #0.1 -> #0.0
  
  Encoder (codec id 86017) not found for output stream #0.0

  I've tried adding a dummy video, but this also failed :

  > ffmpeg -i dummy.mov -i 3139747641.flv movie.swf
  
      
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'dummy.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 512
  
      compatible_brands: qt  
  
      encoder         : Lavf52.52.0
  
      encoder-eng     : Lavf52.52.0
  
    Duration: 00:00:00.10, start: 0.000000, bitrate: 62 kb/s
  
      Stream #0.0(eng): Video: mpeg4, yuv420p, 10x10 [PAR 1:1 DAR 1:1], 1 kb/s, 10 fps, 10 tbr, 10 tbn, 10 tbc
  
  [flv @ 0x8a67fa0]Could not find codec parameters (Video: 0x0000)
  
  [flv @ 0x8a67fa0]Estimating duration from bitrate, this may be inaccurate
  
  Input #1, flv, from '3139747641.flv':
  
    Metadata:
  
      audiocodecid    : -1
  
      duration        : 0
  
      videocodecid    : -1
  
      canSeekToEnd    : true
  
    Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
  
      Stream #1.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
  
      Stream #1.1: Audio: nellymoser, 8000 Hz, mono, s16
  
  picture size invalid (0x0)
  
  Cannot allocate temp picture, check pix fmt

• flv reencode to mp4 for iphone/ipod via ffmpeg and x264 (quality issue)

  3 octobre 2011, par zeroasterisk

  There are a lot of questions on this topic, and I've read most of them and most of the google search results I could come up with.

  When I use FFMPEG to convert a FLV to a iphone3 compatble MP4 file, it just doesn't preserver enough of the quality. Yes, I've worked the hell out of -sameq and -b and -bt settings, text just isn't readable.

  Next I tried to split the video out and process it directly, using these instructions :
  https://sites.google.com/site/linuxencoding/x264-encoding-guide

  The problem is myplayer (via ffmpeg) was not able to determine the duration of the FLV (even though the metadata was set).

  (I assume) Because of that unknown duration, when I create the MP4 file, the resulting x264 file plays through super-fast while the audio plays at the normal rate.

  user@server:/tmp# mplayer -nosound -benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'
  
  MPlayer 1.0rc4-4.4.5 (C) 2000-2010 MPlayer Team
  
  mplayer: could not connect to socket
  
  mplayer: No such file or directory
  
  Failed to open LIRC support. You will not be able to use your remote control.
  
  
  
  Playing input.flv.
  
  libavformat file format detected.
  
  [flv @ 0x1202460]Estimating duration from bitrate, this may be inaccurate
  
  [lavf] stream 0: video (vp6f), -vid 0
  
  [lavf] stream 1: audio (nellymoser), -aid 0
  
  VIDEO:  [VP6F]  1680x992  0bpp  1000.000 fps   33.4 kbps ( 4.1 kbyte/s)
  
  Clip info:
  
   audiocodecid: 6
  
   audiodatarate: 86
  
   audiosamplerate: 44100
  
   audiosamplesize: 16
  
   audiosize: 6097005
  
   canSeekToEnd: true
  
   datasize: 8609138
  
   duration: 567
  
   framerate: 2
  
   hasAudio: true
  
   hasCuePoints: false
  
   hasKeyframes: true
  
   hasMetadata: true
  
   hasVideo: true
  
   height: 992
  
   lasttimestamp: 567
  
   metadatacreator: flvtool++ (Facebook, Motion project, dweatherford)
  
   stereo: false
  
   totalframes: 1043
  
   videocodecid: 4
  
   videodatarate: 33
  
   videosize: 2316256
  
   width: 1680
  
  Using (default) progressive frame mode.Opening video filter: [expand w=640 h=480]
  
  Expand: 640 x 480, -1 ; -1, osd: 0, aspect: 0.000000, round: 1
  
  Opening video filter: [scale w=0 h=0]
  
  Opening video filter: [dsize=640:480:0]
  
  ==========================================================================
  
  Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
  
  Selected video codec: [ffvp6f] vfm: ffmpeg (FFmpeg VP6 Flash)
  
  ==========================================================================
  
  Audio: no sound
  
  Starting playback...
  
  Movie-Aspect is undefined - no prescaling applied.
  
  [swscaler @ 0x7f0c738b9620]Lanczos scaler, from yuv420p to yuv420p using MMX2
  
  VO: [yuv4mpeg] 640x480 => 641x480 Planar YV12

  I have also tried specifying FPS, but no change in results

  user@server:/tmp# mplayer -nosound -fps 25-benchmark -sws 9 -vf dsize=640:480:0,scale=0:0,expand=640:480 -vo yuv4mpeg:file=>(x264 --demuxer y4m --fps 25 --crf 0 --preset slow --threads auto --output output.264 - 2>x264.log) 'input.flv'

  Can someone tell me how to either :

  1. fix my split A/V processing/timing/duration issues ?
  2. improve the
     quality of the FFMPEG conversion of FLV to iphone3 compatible
     format ?