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• how to create or extract a silent mp3 from a video file using ffmpeg or mencoder ? [migrated]

  25 octobre 2011, par mirswith

  I am looking to create an mp3 of silence that is the same duration as the input video file using either ffmpeg or mencoder.

  Using ffmpeg I have tried this :

  ffmpeg -y -i in.avi -ab 8k -ac 1 -vol 0 -acodec libmp3lame out.mp3

  Which works great if the video has an audio track but fails miserably if it does not.

  Any ideas ?

  Thanks !

• Add SRT subtitle to video with ffmpeg

  3 juillet 2015, par jAckOdE

  I use ffmpeg to encode, and add subtitle to a video by following command

  $ ffmpeg -i hifi.avi -i hifi.srt -acodec libfaac -ar 48000 -ab 128k -ac 2 -vcodec libx264 -vpre ipod640 -s 480x240 -b 256k -scodec copy  hifi.m4v -newsubtitle

  Here is the output

  ffmpeg version 0.8.git, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Aug  4 2011 11:11:39 with gcc 4.5.2
  
    configuration: --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --disable-shared --enable-static --enable-gpl --enable-postproc --enable-pthreads --enable-ffplay --disable-ffserver --enable-memalign-hack --enable-nonfree --enable-libfaac --arch=x86 --enable-swscale --enable-libx264 --enable-avfilter --enable-debug=3
  
    libavutil    51. 11. 1 / 51. 11. 1
  
    libavcodec   53.  9. 1 / 53.  9. 1
  
    libavformat  53.  6. 0 / 53.  6. 0
  
    libavdevice  53.  2. 0 / 53.  2. 0
  
    libavfilter   2. 27. 5 /  2. 27. 5
  
    libswscale    2.  0. 0 /  2.  0. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  Input #0, avi, from 'hifi.avi':
  
    Metadata:
  
      encoder         : VirtualDubMod 1.5.4.1 (build 2178/release)
  
      IAS1            : English
  
    Duration: 01:49:02.20, start: 0.000000, bitrate: 897 kb/s
  
      Stream #0.0: Video: mpeg4 (Simple Profile), yuv420p, 544x304 [SAR 1:1 DAR 34:19], 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 32 kb/s
  
  [srt @ 0152c100] Estimating duration from bitrate, this may be inaccurate
  
  Input #1, srt, from 'hifi.srt':
  
    Duration: N/A, start: 56.080000, bitrate: N/A
  
      Stream #1.0: Subtitle: srt
  
  File 'hifi.m4v' already exists. Overwrite ? [y/N] y
  
  [buffer @ 02548920] w:544 h:304 pixfmt:yuv420p tb:1/1000000 sar:1/1 sws_param:
  
  [scale @ 02558ee0] w:544 h:304 fmt:yuv420p -> w:480 h:240 fmt:yuv420p flags:0x4
  
  [libx264 @ 02547f20] Default settings detected, using medium profile
  
  [libx264 @ 02547f20] using SAR=1/1
  
  [libx264 @ 02547f20] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64
  
  [libx264 @ 02547f20] profile High, level 3.0
  
  [libx264 @ 02547f20] 264 - core 115 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=0 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=256 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=10000 vbv_bufsize=10000 nal_hrd=none ip_ratio=1.40 aq=1:1.00
  
  Output #0, ipod, to 'hifi.m4v':
  
      Stream #0.0: Video: libx264, yuv420p, 480x240 [SAR 1:1 DAR 2:1], q=2-31, 256 kb/s, 90k tbn, 25 tbc
  
      Stream #0.1: Audio: libfaac, 48000 Hz, 2 channels, s16, 128 kb/s
  
      Stream #0.2: Subtitle: srt
  
      Stream #0.3: Subtitle: [0][0][0][0] / 0x0000, 64 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
    Stream #1.0 -> #0.2
  
    Stream #1.0 -> #0.3
  
  Encoder (codec id 0) not found for output stream #0.3

  can anyone tell what wrong with my command ??

  thanks,

• FFmpeg on iPhone - Modifying Video Orientation

  6 avril 2015, par Matthew McGoogan

  I’m messing with h264 videos loaded with FFmpeg on the iPhone 3GS. The problem is any videos recorded in "Portrait" orientation have a transformation matrix applied to them causing them to display rotated 90 degrees counter-clock.

  From what I understand thus far, I just need to modify the transform matrix in the ’tkhd’ atom. The problem is I am having trouble accessing or modifying this data. I checked out the FFmpeg implementation for :

  static int mov_read_tkhd(MOVContext *c, ByteIOContext *pb, MOVAtom atom)

  which clearly shows how the matrix is accessed in avformat but when I try to access the header bytes using the same functions I am not getting any rational values. Even if I were to successfully pull the matrix I’m not sure how to replace it ? FFmpeg has functions for retrieving and appending to the track header but nothing for replace it seems ?

  Any help would be greatly appreciated.

  Thanks,
  Matt.