Recherche avancée

Sur d’autres sites (4825)

• No sounds on Apple devices after encoding videos [migrated]

  15 décembre 2013, par Ricardo

  I'm having a problem setting up a media server.
  Everything works just great except the sound of Apple devices, I'm not sure if that's something with "mute" on iOS or our codecs are just not compatible with iOS.

  OS :

  Ubuntu 12.04

  FFMPEG Config :

  ffmpeg version 0.10.8-7:0.10.8-1~lucid1 Copyright 2000-2013 the FFmpeg developers
  
    built on Sep  5 2013 19:50:14 with gcc 4.4.3
  
    configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.8-1~lucid1' --libdir=/usr/lib --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib --enable-shared --disable-static
  
    avcodec     configuration: --arch=amd64 --disable-stripping --enable-pthreads --enable-runtime-cpudetect --extra-version='7:0.10.8-1~lucid1' --libdir=/usr/lib --prefix=/usr --enable-bzlib --enable-libdc1394 --enable-libfreetype --enable-frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libpulse --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-vdpau --enable-libvorbis --enable-libvpx --enable-zlib --enable-gpl --enable-postproc --enable-libcdio --enable-x11grab --enable-libx264 --shlibdir=/usr/lib --enable-shared --disable-static --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb
  
    libavutil      51. 35.100 / 51. 35.100
  
    libavcodec     53. 61.100 / 53. 61.100
  
    libavformat    53. 32.100 / 53. 32.100
  
    libavdevice    53.  4.100 / 53.  4.100
  
    libavfilter     2. 61.100 /  2. 61.100
  
    libswscale      2.  1.100 /  2.  1.100
  
    libswresample   0.  6.100 /  0.  6.100
  
    libpostproc    52.  0.100 / 52.  0.100
  
  Hyper fast Audio and Video encoder

  Codecs :

   D..... = Decoding supported
  
   .E.... = Encoding supported
  
   ..V... = Video codec
  
   ..A... = Audio codec
  
   ..S... = Subtitle codec
  
   ...S.. = Supports draw_horiz_band
  
   ....D. = Supports direct rendering method 1
  
   .....T = Supports weird frame truncation
  
   ------
  
   D V D  4xm             4X Movie
  
   D V D  8bps            QuickTime 8BPS video
  
   D A D  8svx_exp        8SVX exponential
  
   D A D  8svx_fib        8SVX fibonacci
  
    EV    a64multi        Multicolor charset for Commodore 64
  
    EV    a64multi5       Multicolor charset for Commodore 64, extended with 5th color (colram)
  
   DEA D  aac             Advanced Audio Coding
  
   D A D  aac_latm        AAC LATM (Advanced Audio Codec LATM syntax)
  
   D V D  aasc            Autodesk RLE
  
   DEA D  ac3             ATSC A/52A (AC-3)
  
    EA    ac3_fixed       ATSC A/52A (AC-3)
  
   D A D  adpcm_4xm       ADPCM 4X Movie
  
   DEA D  adpcm_adx       SEGA CRI ADX ADPCM
  
   D A D  adpcm_ct        ADPCM Creative Technology
  
   D A D  adpcm_ea        ADPCM Electronic Arts
  
   D A D  adpcm_ea_maxis_xa ADPCM Electronic Arts Maxis CDROM XA
  
   D A D  adpcm_ea_r1     ADPCM Electronic Arts R1
  
   D A D  adpcm_ea_r2     ADPCM Electronic Arts R2
  
   D A D  adpcm_ea_r3     ADPCM Electronic Arts R3
  
   D A D  adpcm_ea_xas    ADPCM Electronic Arts XAS
  
   D A D  adpcm_ima_amv   ADPCM IMA AMV
  
   D A D  adpcm_ima_apc   ADPCM IMA CRYO APC
  
   D A D  adpcm_ima_dk3   ADPCM IMA Duck DK3
  
   D A D  adpcm_ima_dk4   ADPCM IMA Duck DK4
  
   D A D  adpcm_ima_ea_eacs ADPCM IMA Electronic Arts EACS
  
   D A D  adpcm_ima_ea_sead ADPCM IMA Electronic Arts SEAD
  
   D A D  adpcm_ima_iss   ADPCM IMA Funcom ISS
  
   DEA D  adpcm_ima_qt    ADPCM IMA QuickTime
  
   D A D  adpcm_ima_smjpeg ADPCM IMA Loki SDL MJPEG
  
   DEA D  adpcm_ima_wav   ADPCM IMA WAV
  
   D A D  adpcm_ima_ws    ADPCM IMA Westwood
  
   DEA D  adpcm_ms        ADPCM Microsoft
  
   D A D  adpcm_sbpro_2   ADPCM Sound Blaster Pro 2-bit
  
   D A D  adpcm_sbpro_3   ADPCM Sound Blaster Pro 2.6-bit
  
   D A D  adpcm_sbpro_4   ADPCM Sound Blaster Pro 4-bit
  
   DEA D  adpcm_swf       ADPCM Shockwave Flash
  
   D A D  adpcm_thp       ADPCM Nintendo Gamecube THP
  
   D A D  adpcm_xa        ADPCM CDROM XA
  
   DEA D  adpcm_yamaha    ADPCM Yamaha
  
   DEA D  alac            ALAC (Apple Lossless Audio Codec)
  
   D A D  als             MPEG-4 Audio Lossless Coding (ALS)
  
   D A D  amrnb           Adaptive Multi-Rate NarrowBand
  
   D A D  amrwb           Adaptive Multi-Rate WideBand
  
   DEV    amv             AMV Video
  
   D V D  anm             Deluxe Paint Animation
  
   D V D  ansi            ASCII/ANSI art
  
   D A D  ape             Monkey's Audio
  
   DES    ass             Advanced SubStation Alpha subtitle
  
   DEV D  asv1            ASUS V1
  
   DEV D  asv2            ASUS V2
  
   D A D  atrac1          Atrac 1 (Adaptive TRansform Acoustic Coding)
  
   D A D  atrac3          Atrac 3 (Adaptive TRansform Acoustic Coding 3)
  
   D V D  aura            Auravision AURA
  
   D V D  aura2           Auravision Aura 2
  
   DEV D  avrp            Avid 1:1 10-bit RGB Packer
  
   D V D  avs             AVS (Audio Video Standard) video
  
   D V D  bethsoftvid     Bethesda VID video
  
   D V D  bfi             Brute Force & Ignorance
  
   D A D  binkaudio_dct   Bink Audio (DCT)
  
   D A D  binkaudio_rdft  Bink Audio (RDFT)
  
   D V    binkvideo       Bink video
  
   D V D  bintext         Binary text
  
   DEV D  bmp             BMP image
  
   D A D  bmv_audio       Discworld II BMV audio
  
   D V    bmv_video       Discworld II BMV video
  
   D V D  c93             Interplay C93
  
   D V D  camstudio       CamStudio
  
   D V D  camtasia        TechSmith Screen Capture Codec
  
   D V D  cavs            Chinese AVS video (AVS1-P2, JiZhun profile)
  
   D V D  cdgraphics      CD Graphics video
  
   D V D  cinepak         Cinepak
  
   DEV D  cljr            Cirrus Logic AccuPak
  
   D A D  cook            COOK
  
   D V D  cyuv            Creative YUV (CYUV)
  
   DEA D  dca             DCA (DTS Coherent Acoustics)
  
   D V D  dfa             Chronomaster DFA
  
   D V    dirac           BBC Dirac VC-2
  
   DEV D  dnxhd           VC3/DNxHD
  
   DEV    dpx             DPX image
  
   D A D  dsicinaudio     Delphine Software International CIN audio
  
   D V D  dsicinvideo     Delphine Software International CIN video
  
   DES    dvbsub          DVB subtitles
  
   DES    dvdsub          DVD subtitles
  
   DEV D  dvvideo         DV (Digital Video)
  
   D V D  dxa             Feeble Files/ScummVM DXA
  
   D V D  dxtory          Dxtory
  
   DEA D  eac3            ATSC A/52 E-AC-3
  
   D V D  eacmv           Electronic Arts CMV video
  
   D V D  eamad           Electronic Arts Madcow Video
  
   D V D  eatgq           Electronic Arts TGQ video
  
   D V    eatgv           Electronic Arts TGV video
  
   D V D  eatqi           Electronic Arts TQI Video
  
   D V D  escape124       Escape 124
  
   D V D  escape130       Escape 130
  
   DEV D  ffv1            FFmpeg video codec #1
  
   DEVSD  ffvhuff         Huffyuv FFmpeg variant
  
   DEA D  flac            FLAC (Free Lossless Audio Codec)
  
   DEV D  flashsv         Flash Screen Video
  
   DEV D  flashsv2        Flash Screen Video Version 2
  
   D V D  flic            Autodesk Animator Flic video
  
   DEVSD  flv             Flash Video (FLV) / Sorenson Spark / Sorenson H.263
  
   D V D  fraps           Fraps
  
   D V D  frwu            Forward Uncompressed
  
   DEA D  g722            G.722 ADPCM
  
   DEA    g723_1          G.723.1
  
   DEA D  g726            G.726 ADPCM
  
   D A D  g729            G.729
  
   DEV D  gif             GIF (Graphics Interchange Format)
  
   D A D  gsm             GSM
  
   D A D  gsm_ms          GSM Microsoft variant
  
   DEV D  h261            H.261
  
   DEVSDT h263            H.263 / H.263-1996
  
   D VSD  h263i           Intel H.263
  
    EV    h263p           H.263+ / H.263-1998 / H.263 version 2
  
   D V D  h264            H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
   D V D  h264_vdpau      H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (VDPAU acceleration)
  
   DEVSD  huffyuv         Huffyuv / HuffYUV
  
   D V D  idcinvideo      id Quake II CIN video
  
   D V D  idf             iCEDraw text
  
   D V D  iff_byterun1    IFF ByteRun1
  
   D V D  iff_ilbm        IFF ILBM
  
   D A D  imc             IMC (Intel Music Coder)
  
   D V D  indeo2          Intel Indeo 2
  
   D V    indeo3          Intel Indeo 3
  
   D V    indeo4          Intel Indeo Video Interactive 4
  
   D V    indeo5          Intel Indeo Video Interactive 5
  
   D A D  interplay_dpcm  DPCM Interplay
  
   D V D  interplayvideo  Interplay MVE video
  
   DEV    j2k             JPEG 2000
  
   DEV D  jpegls          JPEG-LS
  
   D V D  jv              Bitmap Brothers JV video
  
   D V    kgv1            Kega Game Video
  
   D V D  kmvc            Karl Morton's video codec
  
   D V D  lagarith        Lagarith lossless
  
   DEA D  libgsm          libgsm GSM
  
   DEA D  libgsm_ms       libgsm GSM Microsoft variant
  
    EA    libmp3lame      libmp3lame MP3 (MPEG audio layer 3)
  
   DEA D  libopencore_amrnb OpenCORE Adaptive Multi-Rate (AMR) Narrow-Band
  
   D A D  libopencore_amrwb OpenCORE Adaptive Multi-Rate (AMR) Wide-Band
  
   DEV D  libopenjpeg     OpenJPEG based JPEG 2000 encoder
  
   DEV    libschroedinger libschroedinger Dirac 2.2
  
   DEA D  libspeex        libspeex Speex
  
    EV    libtheora       libtheora Theora
  
    EA    libvorbis       libvorbis Vorbis
  
   DEV    libvpx          libvpx VP8
  
    EV    libx264         libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
  
    EV    libx264rgb      libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 RGB
  
    EV    ljpeg           Lossless JPEG
  
   D V D  loco            LOCO
  
   D A D  mace3           MACE (Macintosh Audio Compression/Expansion) 3:1
  
   D A D  mace6           MACE (Macintosh Audio Compression/Expansion) 6:1
  
   D V D  mdec            Sony PlayStation MDEC (Motion DECoder)
  
   D V D  mimic           Mimic
  
   DEV D  mjpeg           MJPEG (Motion JPEG)
  
   D V D  mjpegb          Apple MJPEG-B
  
   D A D  mlp             MLP (Meridian Lossless Packing)
  
   D V D  mmvideo         American Laser Games MM Video
  
   D V D  motionpixels    Motion Pixels video
  
   D A D  mp1             MP1 (MPEG audio layer 1)
  
   D A D  mp1float        MP1 (MPEG audio layer 1)
  
   DEA D  mp2             MP2 (MPEG audio layer 2)
  
   D A D  mp2float        MP2 (MPEG audio layer 2)
  
   D A D  mp3             MP3 (MPEG audio layer 3)
  
   D A D  mp3adu          ADU (Application Data Unit) MP3 (MPEG audio layer 3)
  
   D A D  mp3adufloat     ADU (Application Data Unit) MP3 (MPEG audio layer 3)
  
   D A D  mp3float        MP3 (MPEG audio layer 3)
  
   D A D  mp3on4          MP3onMP4
  
   D A D  mp3on4float     MP3onMP4
  
   D A D  mpc7            Musepack SV7
  
   D A D  mpc8            Musepack SV8
  
   DEVSDT mpeg1video      MPEG-1 video
  
   D V DT mpeg1video_vdpau MPEG-1 video (VDPAU acceleration)
  
   DEVSDT mpeg2video      MPEG-2 video
  
   DEVSDT mpeg4           MPEG-4 part 2
  
   D V DT mpeg4_vdpau     MPEG-4 part 2 (VDPAU)
  
   D VSDT mpegvideo       MPEG-1 video
  
   D V DT mpegvideo_vdpau MPEG-1/2 video (VDPAU acceleration)
  
   D VSDT mpegvideo_xvmc  MPEG-1/2 video XvMC (X-Video Motion Compensation)
  
   DEVSD  msmpeg4         MPEG-4 part 2 Microsoft variant version 3
  
   D VSD  msmpeg4v1       MPEG-4 part 2 Microsoft variant version 1
  
   DEVSD  msmpeg4v2       MPEG-4 part 2 Microsoft variant version 2
  
   D V D  msrle           Microsoft RLE
  
   DEV D  msvideo1        Microsoft Video-1
  
   D V D  mszh            LCL (LossLess Codec Library) MSZH
  
   D V D  mxpeg           Mobotix MxPEG video
  
   DEA D  nellymoser      Nellymoser Asao
  
   D V D  nuv             NuppelVideo/RTJPEG
  
   DEV D  pam             PAM (Portable AnyMap) image
  
   DEV D  pbm             PBM (Portable BitMap) image
  
   DEA D  pcm_alaw        PCM A-law
  
   D A D  pcm_bluray      PCM signed 16|20|24-bit big-endian for Blu-ray media
  
   D A D  pcm_dvd         PCM signed 20|24-bit big-endian
  
   DEA D  pcm_f32be       PCM 32-bit floating point big-endian
  
   DEA D  pcm_f32le       PCM 32-bit floating point little-endian
  
   DEA D  pcm_f64be       PCM 64-bit floating point big-endian
  
   DEA D  pcm_f64le       PCM 64-bit floating point little-endian
  
   D A D  pcm_lxf         PCM signed 20-bit little-endian planar
  
   DEA D  pcm_mulaw       PCM mu-law
  
   DEA D  pcm_s16be       PCM signed 16-bit big-endian
  
   DEA D  pcm_s16le       PCM signed 16-bit little-endian
  
   D A D  pcm_s16le_planar PCM 16-bit little-endian planar
  
   DEA D  pcm_s24be       PCM signed 24-bit big-endian
  
   DEA D  pcm_s24daud     PCM D-Cinema audio signed 24-bit
  
   DEA D  pcm_s24le       PCM signed 24-bit little-endian
  
   DEA D  pcm_s32be       PCM signed 32-bit big-endian
  
   DEA D  pcm_s32le       PCM signed 32-bit little-endian
  
   DEA D  pcm_s8          PCM signed 8-bit
  
   D A D  pcm_s8_planar   PCM signed 8-bit planar
  
   DEA D  pcm_u16be       PCM unsigned 16-bit big-endian
  
   DEA D  pcm_u16le       PCM unsigned 16-bit little-endian
  
   DEA D  pcm_u24be       PCM unsigned 24-bit big-endian
  
   DEA D  pcm_u24le       PCM unsigned 24-bit little-endian
  
   DEA D  pcm_u32be       PCM unsigned 32-bit big-endian
  
   DEA D  pcm_u32le       PCM unsigned 32-bit little-endian
  
   DEA D  pcm_u8          PCM unsigned 8-bit
  
   D A D  pcm_zork        PCM Zork
  
   DEV D  pcx             PC Paintbrush PCX image
  
   DEV D  pgm             PGM (Portable GrayMap) image
  
   DEV D  pgmyuv          PGMYUV (Portable GrayMap YUV) image
  
   D S    pgssub          HDMV Presentation Graphic Stream subtitles
  
   D V D  pictor          Pictor/PC Paint
  
   DEV D  png             PNG image
  
   DEV D  ppm             PPM (Portable PixelMap) image
  
   DEV D  prores          Apple ProRes
  
   D V D  prores_lgpl     Apple ProRes (iCodec Pro)
  
   D V D  ptx             V.Flash PTX image
  
   D A D  qcelp           QCELP / PureVoice
  
   D A D  qdm2            QDesign Music Codec 2
  
   D V D  qdraw           Apple QuickDraw
  
   D V D  qpeg            Q-team QPEG
  
   DEV D  qtrle           QuickTime Animation (RLE) video
  
   DEV D  r10k            AJA Kona 10-bit RGB Codec
  
   DEV D  r210            Uncompressed RGB 10-bit
  
   DEV    rawvideo        raw video
  
   DEA D  real_144        RealAudio 1.0 (14.4K) encoder
  
   D A D  real_288        RealAudio 2.0 (28.8K)
  
   D V D  rl2             RL2 video
  
   DEA D  roq_dpcm        id RoQ DPCM
  
   DEV D  roqvideo        id RoQ video
  
   D V D  rpza            QuickTime video (RPZA)
  
   DEV D  rv10            RealVideo 1.0
  
   DEV D  rv20            RealVideo 2.0
  
   D V D  rv30            RealVideo 3.0
  
   D V D  rv40            RealVideo 4.0
  
   D A D  s302m           SMPTE 302M
  
   DEV    sgi             SGI image
  
   D A D  shorten         Shorten
  
   D A D  sipr            RealAudio SIPR / ACELP.NET
  
   D A D  smackaud        Smacker audio
  
   D V D  smackvid        Smacker video
  
   D V D  smc             QuickTime Graphics (SMC)
  
   DEV D  snow            Snow
  
   D A D  sol_dpcm        DPCM Sol
  
   DEA D  sonic           Sonic
  
    EA    sonicls         Sonic lossless
  
   D V D  sp5x            Sunplus JPEG (SP5X)
  
   DES    srt             SubRip subtitle
  
   D V D  sunrast         Sun Rasterfile image
  
   DEV D  svq1            Sorenson Vector Quantizer 1 / Sorenson Video 1 / SVQ1
  
   D VSD  svq3            Sorenson Vector Quantizer 3 / Sorenson Video 3 / SVQ3
  
   DEV D  targa           Truevision Targa image
  
   D VSD  theora          Theora
  
   D V D  thp             Nintendo Gamecube THP video
  
   D V D  tiertexseqvideo Tiertex Limited SEQ video
  
   DEV D  tiff            TIFF image
  
   D V D  tmv             8088flex TMV
  
   D A D  truehd          TrueHD
  
   D V D  truemotion1     Duck TrueMotion 1.0
  
   D V D  truemotion2     Duck TrueMotion 2.0
  
   D A D  truespeech      DSP Group TrueSpeech
  
   D A D  tta             True Audio (TTA)
  
   D A D  twinvq          VQF TwinVQ
  
   D V D  txd             Renderware TXD (TeXture Dictionary) image
  
   D V D  ultimotion      IBM UltiMotion
  
   D V D  utvideo         Ut Video
  
   DEV D  v210            Uncompressed 4:2:2 10-bit
  
   D V D  v210x           Uncompressed 4:2:2 10-bit
  
   DEV D  v308            Uncompressed packed 4:4:4
  
   DEV D  v410            Uncompressed 4:4:4 10-bit
  
   D V    vb              Beam Software VB
  
   D V D  vble            VBLE Lossless Codec
  
   D V D  vc1             SMPTE VC-1
  
   D V D  vc1_vdpau       SMPTE VC-1 VDPAU
  
   D V D  vc1image        Windows Media Video 9 Image v2
  
   D V D  vcr1            ATI VCR1
  
   D A D  vmdaudio        Sierra VMD audio
  
   D V D  vmdvideo        Sierra VMD video
  
   D V D  vmnc            VMware Screen Codec / VMware Video
  
   DEA D  vorbis          Vorbis
  
   D VSD  vp3             On2 VP3
  
   D V D  vp5             On2 VP5
  
   D V D  vp6             On2 VP6
  
   D V D  vp6a            On2 VP6 (Flash version, with alpha channel)
  
   D V D  vp6f            On2 VP6 (Flash version)
  
   D V D  vp8             On2 VP8
  
   D V D  vqavideo        Westwood Studios VQA (Vector Quantized Animation) video
  
   D A D  wavesynth       Wave synthesis pseudo-codec
  
   D A D  wavpack         WavPack
  
   D A    wmalossless     Windows Media Audio 9 Lossless
  
   D A D  wmapro          Windows Media Audio 9 Professional
  
   DEA D  wmav1           Windows Media Audio 1
  
   DEA D  wmav2           Windows Media Audio 2
  
   D A D  wmavoice        Windows Media Audio Voice
  
   DEVSD  wmv1            Windows Media Video 7
  
   DEVSD  wmv2            Windows Media Video 8
  
   D V D  wmv3            Windows Media Video 9
  
   D V D  wmv3_vdpau      Windows Media Video 9 VDPAU
  
   D V D  wmv3image       Windows Media Video 9 Image
  
   D V D  wnv1            Winnov WNV1
  
   D A D  ws_snd1         Westwood Audio (SND1)
  
   D A D  xan_dpcm        DPCM Xan
  
   D V D  xan_wc3         Wing Commander III / Xan
  
   D V D  xan_wc4         Wing Commander IV / Xxan
  
   D V D  xbin            eXtended BINary text
  
   D V D  xl              Miro VideoXL
  
   DES    xsub            DivX subtitles (XSUB)
  
   DEV D  xwd             XWD (X Window Dump) image
  
   DEV D  y41p            Uncompressed YUV 4:1:1 12-bit
  
   D V    yop             Psygnosis YOP Video
  
   DEV D  yuv4            Uncompressed packed 4:2:0
  
   DEV D  zlib            LCL (LossLess Codec Library) ZLIB
  
   DEV D  zmbv            Zip Motion Blocks Video

  Library we use to convert :

  public function getAvailableAudioCodecs()
  
      {
  
          return array('libvo_aacenc', 'libfaac', 'libmp3lame');
  
      }

  By default I use 'libmp3lame' now because 'libfaac' is not supported by ffmpeg
  and when Im trying to encode sound by libfaac I'm getting that codec not found

  Thanks in advance !

• WebVTT as a W3C Recommendation

  1er janvier 2014, par silvia

  Three weeks ago I attended TPAC, the annual meeting of W3C Working Groups. One of the meetings was of the Timed Text Working Group (TT-WG), that has been specifying TTML, the Timed Text Markup Language. It is now proposed that WebVTT be also standardised through the same Working Group.

  How did that happen, you may ask, in particular since WebVTT and TTML have in the past been portrayed as rival caption formats ? How will the WebVTT spec that is currently under development in the Text Track Community Group (TT-CG) move through a Working Group process ?

  I’ll explain first why there is a need for WebVTT to become a W3C Recommendation, and then how this is proposed to be part of the Timed Text Working Group deliverables, and finally how I can see this working between the TT-CG and the TT-WG.

  Advantages of a W3C Recommendation

  TTML is a XML-based markup format for captions developed during the time that XML was all the hotness. It has become a W3C standard (a so-called “Recommendation”) despite not having been implemented in any browsers (if you ask me : that’s actually a flaw of the W3C standardisation process : it requires only two interoperable implementations of any kind – and that could be anyone’s JavaScript library or Flash demonstrator – it doesn’t actually require browser implementations. But I digress…). To be fair, a subpart of TTML is by now implemented in Internet Explorer, but all the other major browsers have thus far rejected proposals of implementation.

  Because of its Recommendation status, TTML has become the basis for several other caption standards that other SDOs have picked : the SMPTE’s SMPTE-TT format, the EBU’s EBU-TT format, and the DASH Industry Forum’s use of SMPTE-TT. SMPTE-TT has also become the “safe harbour” format for the US legislation on captioning as decided by the FCC. (Note that the FCC requirements for captions on the Web are actually based on a list of features rather than requiring a specific format. But that will be the topic of a different blog post…)

  WebVTT is much younger than TTML. TTML was developed as an interchange format among caption authoring systems. WebVTT was built for rendering in Web browsers and with HTML5 in mind. It meets the requirements of the <track> element and supports more than just captions/subtitles. WebVTT is popular with browser developers and has already been implemented in all major browsers (Firefox Nightly is the last to implement it – all others have support already released).

  As we can see and as has been proven by the HTML spec and multiple other specs : browsers don’t wait for specifications to have W3C Recommendation status before they implement them. Nor do they really care about the status of a spec – what they care about is whether a spec makes sense for the Web developer and user communities and whether it fits in the Web platform. WebVTT has obviously achieved this status, even with an evolving spec. (Note that the spec tries very hard not to break backwards compatibility, thus all past implementations will at least be compatible with the more basic features of the spec.)

  Given that Web browsers don’t need WebVTT to become a W3C standard, why then should we spend effort in moving the spec through the W3C process to become a W3C Recommendation ?

  The modern Web is now much bigger than just Web browsers. Web specifications are being used in all kinds of devices including TV set-top boxes, phone and tablet apps, and even unexpected devices such as white goods. Videos are increasingly omnipresent thus exposing deaf and hard-of-hearing users to ever-growing challenges in interacting with content on diverse devices. Some of these devices will not use auto-updating software but fixed versions so can’t easily adapt to new features. Thus, caption producers (both commercial and community) need to be able to author captions (and other video accessibility content as defined by the HTML5 element) towards a feature set that is clearly defined to be supported by such non-updating devices.

  Understandably, device vendors in this space have a need to build their technology on standardised specifications. SDOs for such device technologies like to reference fixed specifications so the feature set is not continually updating. To reference WebVTT, they could use a snapshot of the specification at any time and reference that, but that’s not how SDOs work. They prefer referencing an officially sanctioned and tested version of a specification – for a W3C specification that means creating a W3C Recommendation of the WebVTT spec.

  Taking WebVTT on a W3C recommendation track is actually advantageous for browsers, too, because a test suite will have to be developed that proves that features are implemented in an interoperable manner. In summary, I can see the advantages and personally support the effort to take WebVTT through to a W3C Recommendation.

  Choice of Working Group

  FAIK this is the first time that a specification developed in a Community Group is being moved into the recommendation track. This is something that has been expected when the W3C created CGs, but not something that has an established process yet.

  The first question of course is which WG would take it through to Recommendation ? Would we create a new Working Group or find an existing one to move the specification through ? Since WGs involve a lot of overhead, the preference was to add WebVTT to the charter of an existing WG. The two obvious candidates were the HTML WG and the TT-WG – the first because it’s where WebVTT originated and the latter because it’s the closest thematically.

  Adding a deliverable to a WG is a major undertaking. The TT-WG is currently in the process of re-chartering and thus a suggestion was made to add WebVTT to the milestones of this WG. TBH that was not my first choice. Since I’m already an editor in the HTML WG and WebVTT is very closely related to HTML and can be tested extensively as part of HTML, I preferred the HTML WG. However, adding WebVTT to the TT-WG has some advantages, too.

  Since TTML is an exchange format, lots of captions that will be created (at least professionally) will be in TTML and TTML-related formats. It makes sense to create a mapping from TTML to WebVTT for rendering in browsers. The expertise of both, TTML and WebVTT experts is required to develop a good mapping – as has been shown when we developed the mapping from CEA608/708 to WebVTT. Also, captioning experts are already in the TT-WG, so it helps to get a second set of eyes onto WebVTT.

  A disadvantage of moving a specification out of a CG into a WG is, however, that you potentially lose a lot of the expertise that is already involved in the development of the spec. People don’t easily re-subscribe to additional mailing lists or want the additional complexity of involving another community (see e.g. this email).

  So, a good process needs to be developed to allow everyone to contribute to the spec in the best way possible without requiring duplicate work. How can we do that ?

  The forthcoming process

  At TPAC the TT-WG discussed for several hours what the next steps are in taking WebVTT through the TT-WG to recommendation status (agenda with slides). I won’t bore you with the different views – if you are keen, you can read the minutes.

  What I came away with is the following process :

  1. Fix a few more bugs in the CG until we’re happy with the feature set in the CG. This should match the feature set that we realistically expect devices to implement for a first version of the WebVTT spec.
  2. Make a FSA (Final Specification Agreement) in the CG to create a stable reference and a clean IPR position.
  3. Assuming that the TT-WG’s charter has been approved with WebVTT as a milestone, we would next bring the FSA specification into the TT-WG as FPWD (First Public Working Draft) and immediately do a Last Call which effectively freezes the feature set (this is possible because there has already been wide community review of the WebVTT spec) ; in parallel, the CG can continue to develop the next version of the WebVTT spec with new features (just like it is happening with the HTML5 and HTML5.1 specifications).
  4. Develop a test suite and address any issues in the Last Call document (of course, also fix these issues in the CG version of the spec).
  5. As per W3C process, substantive and minor changes to Last Call documents have to be reported and raised issues addressed before the spec can progress to the next level : Candidate Recommendation status.
  6. For the next step – Proposed Recommendation status – an implementation report is necessary, and thus the test suite needs to be finalized for the given feature set. The feature set may also be reduced at this stage to just the ones implemented interoperably, leaving any other features for the next version of the spec.
  7. The final step is Recommendation status, which simply requires sufficient support and endorsement by W3C members.

  The first version of the WebVTT spec naturally has a focus on captioning (and subtitling), since this has been the dominant use case that we have focused on this far and it’s the part that is the most compatibly implemented feature set of WebVTT in browsers. It’s my expectation that the next version of WebVTT will have a lot more features related to audio descriptions, chapters and metadata. Thus, this seems a good time for a first version feature freeze.

  There are still several obstacles towards progressing WebVTT as a milestone of the TT-WG. Apart from the need to get buy-in from the TT-WG, the TT-CG, and the AC (Adivisory Committee who have to approve the new charter), we’re also looking at the license of the specification document.

  The CG specification has an open license that allows creating derivative work as long as there is attribution, while the W3C document license for documents on the recommendation track does not allow the creation of derivative work unless given explicit exceptions. This is an issue that is currently being discussed in the W3C with a proposal for a CC-BY license on the Recommendation track. However, my view is that it’s probably ok to use the different document licenses : the TT-WG will work on WebVTT 1.0 and give it a W3C document license, while the CG starts working on the next WebVTT version under the open CG license. It probably actually makes sense to have a less open license on a frozen spec.

  Making the best of a complicated world

  WebVTT is now proposed as part of the recharter of the TT-WG. I have no idea how complicated the process will become to achieve a W3C WebVTT 1.0 Recommendation, but I am hoping that what is outlined above will be workable in such a way that all of us get to focus on progressing the technology.

  At TPAC I got the impression that the TT-WG is committed to progressing WebVTT to Recommendation status. I know that the TT-CG is committed to continue developing WebVTT to its full potential for all kinds of media-time aligned content with new kinds already discussed at FOMS. Let’s enable both groups to achieve their goals. As a consequence, we will allow the two formats to excel where they do : TTML as an interchange format and WebVTT as a browser rendering format.

• How do i convert a transparent .mov-file to an mp4 file overlayed on a background-image using FFMPEG [migrated]

  5 mars 2013, par Ernie

  I'm trying to convert a mov file with the following specs :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mov':
  
  Metadata:
  
      major_brand     : qt  
  
      minor_version   : 537199360
  
      compatible_brands: qt  
  
      creation_time   : 2012-10-09 13:34:01
  
  Duration: 00:00:51.60, start: 0.000000, bitrate: 217433 kb/s
  
      Stream #0:0(eng): Video: prores (ap4h / 0x68347061), yuv444p10le, 1920x1080, 215844 kb/s, SAR 1:1 DAR 16:9, 25 fps, 25 tbr, 25 tbn, 25 tbc
  
      Metadata:
  
          creation_time   : 2012-10-09 13:34:01
  
          handler_name    : Apple Alias Data Handler
  
          timecode        : 01:00:00:00
  
      Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s
  
      Metadata:
  
          creation_time   : 2012-10-09 13:34:01
  
          handler_name    : Apple Alias Data Handler
  
      Stream #0:2(eng): Data: none (tmcd / 0x64636D74)
  
      Metadata:
  
          creation_time   : 2012-10-09 13:42:30
  
          handler_name    : Apple Alias Data Handler
  
          timecode        : 01:00:00:00

  I want a background-image with that video on top of it and save it as an mp4-file. In the meantime the video has to be scaled and cropped
  I need a solution which can be automated and placed on a server, that is why i tried ffmpeg

  This is wat have at the moment :

  ffmpeg -loop 1 -f image2 -i background.png -r 25 -an -vcodec libx264 -b:v 1500k -vf "movie=test.mov[movie];[movie]scale=max(552\, 420*iw/ih):-1[OUT1]; [OUT1]crop=552:420[OUT2]; [0][OUT2] overlay=0:0 [out]" -s 552x420 -y output.mp4

  The problem is, somehow, the transparency is lost, and the background is black, instead of the underlying image. When i try the same ffmpeg command with a transparent FLV as input, it works, but i would like it to work without having to convert al source files first to another format

  Any help with this would be greatly appreciated !

  This is my current ffmpeg configuration :

  ffmpeg version 1.1.2 Copyright (c) 2000-2013 the FFmpeg developers
  
  built on Mar  4 2013 11:19:29 with Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
  
  configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libfreetype --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-nonfree --enable-libfaac
  
      libavutil      52. 13.100 / 52. 13.100
  
      libavcodec     54. 86.100 / 54. 86.100
  
      libavformat    54. 59.106 / 54. 59.106
  
      libavdevice    54.  3.102 / 54.  3.102
  
      libavfilter     3. 32.100 /  3. 32.100
  
      libswscale      2.  1.103 /  2.  1.103
  
      libswresample   0. 17.102 /  0. 17.102
  
      libpostproc    52.  2.100 / 52.  2.100