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• Dreamcast Track Sizes

  1er mars 2015, par Multimedia Mike — Sega Dreamcast

  I’ve been playing around with Sega Dreamcast discs lately. Not playing the games on the DC discs, of course, just studying their structure. To review, the Sega Dreamcast game console used special optical discs named GD-ROMs, where the GD stands for “gigadisc”. They are capable of holding about 1 gigabyte of data.

  You know what’s weird about these discs ? Each one manages to actually store a gigabyte of data. Each disc has a CD portion and a GD portion. The CD portion occupies the first 45000 sectors and can be read in any standard CD drive. This area is divided between a brief data track and a brief (usually) audio track.

  The GD region starts at sector 45000. Sometimes, it’s just one humongous data track that consumes the entire GD region. More often, however, the data track is split between the first track and the last track in the region and there are 1 or more audio tracks in between. But the weird thing is, the GD region is always full. I made a study of it (click for a larger, interactive graph) :

  
  
  

  Some discs put special data or audio bonuses in the CD region for players to discover. But every disc manages to fill out the GD region. I checked up on a lot of those audio tracks that divide the GD data and they’re legitimate music tracks. So what’s the motivation ? Why would the data track be split in 2 pieces like that ?

  I eventually realized that I probably answered this question in this blog post from 4 years ago. The read speed from the outside of an optical disc is higher than the inside of the same disc. When I inspect the outer data tracks of some of these discs, sure enough, there seem to be timing-sensitive multimedia FMV files living on the outer stretches.

  One day, I’ll write a utility to take apart the split ISO-9660 filesystem offset from a weird sector.

• ffmpeg - extract timecode start metadata from tmcd track to a drawtext filter

  3 mars 2015, par mwjb

  I have a Quicktime file with a timecode track. I’m encoding it to a new video codec and would like to burnin the timecode from timecode track. Setting the timecode manually isn’t an option as this will be used for many files with unique starting timecodes.

  This is the current work-in-progress ffmpeg command. Obviously I need to find a way to extract the metadate:timecode value and have this start the timecode count instead of the manual entry seen below :

  ffmpeg -i infile.mov -y -c:v mjpeg -qscale:v 4 -vendor ap10 -pix_fmt yuvj422p -s 1280x720 -vf drawtext="fontfile=thefont.ttf: timecode='01\:00\:00\:00': rate=24: fontsize=40: fontcolor=white: boxcolor=black: box=1: x=1700: y=80" outfile.mov

  The Timecode metadata is there in the Stream #0:1 track, as read by ffmpeg :

  ffmpeg version 2.5.2 Copyright (c) 2000-2014 the FFmpeg developers
  
    built on Jan  1 2015 20:24:48 with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  
  configuration: --prefix=/Volumes/tempdisk/sw --as=yasm --enable-gpl --enable-pthreads --disable-ffplay --disable-ffserver --disable-shared --enable-static --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libx265 --enable-libxvid --enable-zlib --enable-avfilter --enable-fontconfig --enable-libfreetype --enable-libass --enable-libutvideo --enable-filters --enable-postproc --enable-runtime-cpudetect
  
  libavutil      54. 15.100 / 54. 15.100
  
  libavcodec     56. 13.100 / 56. 13.100
  
  libavformat    56. 15.102 / 56. 15.102
  
  libavdevice    56.  3.100 / 56.  3.100
  
  libavfilter     5.  2.103 /  5.  2.103
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  1.100 /  1.  1.100
  
  libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'infile.mov':
  
    Metadata:
  
  major_brand     : qt  
  
  minor_version   : 537199360
  
  compatible_brands: qt  
  
  creation_time   : 2015-03-02 22:06:00
  
  timecode        : 06:00:00:00
  
  Duration: 00:20:00.00, start: 0.000000, bitrate: 36175 kb/s
  
  Stream #0:0(eng): Video: dnxhd (AVdn / 0x6E645641), yuv422p, 1920x1080, 36175 kb/s, 24 fps, 24 tbr, 24k tbn, 24k tbc (default)
  
  Metadata:
  
    creation_time   : 2015-03-02 22:06:00
  
    handler_name    : Apple Alias Data Handler
  
    encoder         : Avid DNxHD Codec
  
  Stream #0:1(eng): Data: none (tmcd / 0x64636D74) (default)
  
  Metadata:
  
    creation_time   : 2015-03-02 22:06:58
  
    handler_name    : Apple Alias Data Handler
  
    timecode        : 06:00:00:00

  I came across this post ffmpeg and timecode from movie metadata which appeared to be on the same sort of track as I’m on. Would certainly appreciate some guidance on this. Many Thanks.

• FFMpeg is slow on Android [duplicate]

  28 juin 2017, par Oleg Filimonov

  This question already has an answer here :

  • Precompiled FFmpeg for android versus building FFmpeg using android NDK
    
    2 answers
    
  • Fast Video Compression on Android
    
    2 answers
    

  I’m using this library : https://github.com/WritingMinds/ffmpeg-android

  Executing this command :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast out.mp4

  (Basically add a bunch of animated overlays to the video)

  On PC this command takes about a second to execute (render speed is about 278 fps). But on Android device with Snapdragon 821 it takes about 10 seconds (about 30 fps).

  The curious thing is that whenever command is executing on PC, CPU load is around 90%, but on Android it’s less than 1% (see screenshot : initial spike is UI stuff plus loading binaries, afterwards ffmpeg was executing until 10 second mark)

  

  I tried executing the same command, but writing to /dev/null
  instead of the file :

  ffmpeg -y -i video.mp4 -ignore_loop 0 -i overlay.gif -filter_complex `
  
  >> "[0][1]overlay=x=mod((1080/4 + sin(t)*1080/4)\,1920):y=mod(t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*1 + 1080/4 - sin(2*t)*1080/4)\,1920):y=mod(100 + t*300\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*2 + 1080/4 - sin(-90 + t/2)*1080/4)\,1920):y=mod(150 + t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*3 + 1080/4 - sin(90 + 3*t)*1080/4)\,1920):y=mod(200 + t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*4 + 1080/4 - sin(180 + t)*1080/4)\,1920):y=mod(t*250\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*5 + 1080/4 - sin(-180 + t)*1080/4)\,1920):y=mod(t*100\,1080):shortest=1[res];`
  
  >> [res][1]overlay=x=mod((200*6 + 1080/4 - sin(2*t)*1080/4)\,1920):y=100 + mod(100 + t*300\,1080):shortest=1[res]`
  
  >> " -map "[res]" -preset ultrafast -f null /dev/null

  This reduced time by 3 seconds.

  I also tried replacing gif overlay with png overlay, but speed didn’t improve significantly.

  Here’s log of the command execution on Android :

  ffmpeg version n3.0.1 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with gcc 4.8 (GCC)
  
    configuration: --target-os=linux --cross-prefix=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi- --arch=arm --cpu=cortex-a8 --enable-runtime-cpudetect --sysroot=/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/sysroot --enable-pic --enable-libx264 --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-fontconfig --enable-pthreads --disable-debug --disable-ffserver --enable-version3 --enable-hardcoded-tables --disable-ffplay --disable-ffprobe --enable-gpl --enable-yasm --disable-doc --disable-shared --enable-static --pkg-config=/home/vagrant/SourceCode/ffmpeg-android/ffmpeg-pkg-config --prefix=/home/vagrant/SourceCode/ffmpeg-android/build/armeabi-v7a --extra-cflags='-I/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/include -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fno-strict-overflow -fstack-protector-all' --extra-ldflags='-L/home/vagrant/SourceCode/ffmpeg-android/toolchain-android/lib -Wl,-z,relro -Wl,-z,now -pie' --extra-libs='-lpng -lexpat -lm' --extra-cxxflags=
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/data/user/0/com.example.user.proofofconcept/files/in_10s.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      creation_time   : 2017-06-27 18:07:54
  
    Duration: 00:00:10.47, start: 0.000000, bitrate: 14043 kb/s
  
      Stream #0:0(eng): Video: h264 (Baseline) (avc1 / 0x31637661), yuvj420p(pc, smpte170m), 1280x720, 13971 kb/s, 29.86 fps, 30.01 tbr, 90k tbn, 180k tbc (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:53
  
        handler_name    : VideoHandle
  
      Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 96 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-06-27 18:07:54
  
        handler_name    : SoundHandle
  
  Input #1, gif, from '/data/user/0/com.example.user.proofofconcept/files/overlay.gif':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Video: gif, bgra, 130x98, 6.17 fps, 4.92 tbr, 100 tbn, 100 tbc
  
  [swscaler @ 0xeddb3000] deprecated pixel format used, make sure you did set range correctly
  
  [libx264 @ 0xee1fdc00] using cpu capabilities: none!
  
  [libx264 @ 0xee1fdc00] profile Constrained Baseline, level 3.2
  
  [libx264 @ 0xee1fdc00] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  Output #0, mp4, to '/storage/emulated/0/temp/out.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=-1--1, 30.01 fps, 90k tbn, 30.01 tbc (default)
  
      Metadata:
  
        encoder         : Lavc57.24.102 libx264
  
      Side data:
  
        unknown side data type 10 (24 bytes)
  
  Stream mapping:
  
    Stream #0:0 (h264) -> overlay:main
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    Stream #1:0 (gif) -> overlay:overlay
  
    overlay -> Stream #0:0 (libx264)
  
  Press [q] to stop, [?] for help
  
  frame=   16 fps=0.0 q=24.0 size=     227kB time=00:00:00.29 bitrate=6210.2kbits/s dup=2 drop=0 speed=0.56x    
  
  frame=   29 fps= 28 q=24.0 size=     451kB time=00:00:00.73 bitrate=5042.1kbits/s dup=2 drop=0 speed=0.707x    
  
  frame=   40 fps= 26 q=24.0 size=     637kB time=00:00:01.09 bitrate=4744.5kbits/s dup=2 drop=0 speed=0.71x    
  
  frame=   57 fps= 28 q=24.0 size=     903kB time=00:00:01.66 bitrate=4441.3kbits/s dup=2 drop=0 speed=0.812x    
  
  frame=   75 fps= 29 q=24.0 size=    1186kB time=00:00:02.26 bitrate=4288.0kbits/s dup=2 drop=0 speed=0.885x    
  
  frame=   94 fps= 31 q=24.0 size=    1456kB time=00:00:02.89 bitrate=4113.4kbits/s dup=2 drop=0 speed=0.945x    
  
  frame=  113 fps= 32 q=25.0 size=    1780kB time=00:00:03.53 bitrate=4127.3kbits/s dup=2 drop=0 speed=0.985x    
  
  frame=  131 fps= 32 q=24.0 size=    2101kB time=00:00:04.13 bitrate=4165.9kbits/s dup=2 drop=0 speed=1.01x    
  
  frame=  150 fps= 33 q=24.0 size=    2461kB time=00:00:04.76 bitrate=4231.2kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  165 fps= 32 q=24.0 size=    2721kB time=00:00:05.26 bitrate=4234.1kbits/s dup=2 drop=0 speed=1.03x    
  
  frame=  185 fps= 33 q=24.0 size=    3028kB time=00:00:05.93 bitrate=4182.4kbits/s dup=2 drop=0 speed=1.05x    
  
  frame=  205 fps= 33 q=24.0 size=    3329kB time=00:00:06.59 bitrate=4133.3kbits/s dup=2 drop=0 speed=1.07x    
  
  frame=  224 fps= 34 q=24.0 size=    3610kB time=00:00:07.23 bitrate=4089.7kbits/s dup=2 drop=0 speed=1.08x    
  
  frame=  243 fps= 34 q=24.0 size=    3901kB time=00:00:07.86 bitrate=4063.3kbits/s dup=2 drop=0 speed=1.09x    
  
  frame=  264 fps= 34 q=24.0 size=    4297kB time=00:00:08.56 bitrate=4110.6kbits/s dup=2 drop=0 speed=1.11x    
  
  frame=  284 fps= 35 q=24.0 size=    4601kB time=00:00:09.23 bitrate=4083.5kbits/s dup=2 drop=0 speed=1.12x    
  
  frame=  304 fps= 35 q=24.0 size=    4886kB time=00:00:09.89 bitrate=4044.4kbits/s dup=2 drop=0 speed=1.14x    
  
  frame=  314 fps= 35 q=-1.0 Lsize=    5138kB time=00:00:10.46 bitrate=4022.4kbits/s dup=2 drop=0 speed=1.16x    
  
  video:5135kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.040961%
  
  [libx264 @ 0xee1fdc00] frame I:2     Avg QP:20.50  size: 84700
  
  [libx264 @ 0xee1fdc00] frame P:312   Avg QP:24.06  size: 16310
  
  [libx264 @ 0xee1fdc00] mb I  I16..4: 100.0%  0.0%  0.0%
  
  [libx264 @ 0xee1fdc00] mb P  I16..4:  7.7%  0.0%  0.0%  P16..4: 54.9%  0.0%  0.0%  0.0%  0.0%    skip:37.4%
  
  [libx264 @ 0xee1fdc00] coded y,uvDC,uvAC intra: 62.7% 22.9% 3.4% inter: 26.1% 8.4% 0.9%
  
  [libx264 @ 0xee1fdc00] i16 v,h,dc,p: 13% 14% 59% 13%
  
  [libx264 @ 0xee1fdc00] i8c dc,h,v,p: 47% 24% 22%  6%
  
  [libx264 @ 0xee1fdc00] kb/s:4020.26
  
   Success
  
  time used: 9843

  So what could be the reason of such low CPU load ?