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• 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.

• 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,

• How to encode a stream of RGBA values to video ?

  20 septembre 2011, par Rob Oplawar

  More specifically :
  I have a sequence of 32 bit unsigned RGBA integers for pixels- e.g. 640 integers per row starting at the left pixel, 480 rows per frame starting at the top row, repeat for n frames. Is there an easy way to feed this to ffmpeg (or some other encoder) without first encoding it to a common image format ?

  I'm assuming ffmpeg is the best tool for me to use in this case, but I'm open to suggestions (the output video format doesn't matter too much).

  ---

  I know the documentation would enlighten me if I just knew the right keywords... In case I'm asking the wrong question, here's what I'm trying to do at the highest level :

  I have some Actionscript code that draws and animates on the display tree, and I've wrapped it in an AIR application that draws BitmapData frame-by-frame. AIR has proved to be woefully inefficient at directly encoding this output- the best I've managed is a few frames per second, and I need to render at least 15 fps, preferably more like 100 fps, which I get out of ffmpeg when I feed it PNG images (AIR can take 1+ seconds to encode one 640x480 png... appalling). Instead of encoding inside AIR I can send the raw byte data out to an encoder or to disk as fast as it's rendered.

  If you're wondering why I'm using Actionscript to render an animation or why it has to be encoded quickly, don't. Suffice it to say, the frames are computed at execution time (not stored as an animation in a .swf file, for example), I have a very large amount of video to create and limited time to do so, and using something other than Actionscript to produce the frames is not an option.