• Compression Techniques

  cutting iFrame only media

  Posted by Mohammad Torabi on April 28, 2015 at 5:13 pm

  Hi,

  I have created an iFrame only MXF file by the command below using FFmpeg:

  value of -ss and -t is base on nearest iFrame before the mark-in and after mark-out.

  [code]ffmpeg -ss 3020.58 -i “input file name.MXF” -t 20.5205 -threads 4 -pix_fmt yuv420p
  -flags +ildct+ilme -vcodec mpeg2video -top 1 -dc 10 -intra_vlc 1 -qmin 1 -lmin 1*QP2LAMBDA -vtag xd5c -g 0 -rc_max_vbv_use 1 -rc_min_vbv_use 1 -b:v 35000k -bufsize 35000k -minrate 35000k -maxra
  te 35000k -aspect 16:9 -vf “scale=-1:1080” -r 29.97 -f mxf -y “iFrame Only output file name.MXF”
  [/code]

  the log of running command is below:

  [code]ffmpeg version N-71737-gb410c69 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.2 (GCC)
  configuration: –enable-gpl –enable-version3 –disable-w32threads –enable-avisynth –enable-bzlib –enable-fontconfig –enable-frei0r –enable-gnutls –enable-iconv –enable-libass –enable
  -libbluray –enable-libbs2b –enable-libcaca –enable-libdcadec –enable-libfreetype –enable-libgme –enable-libgsm –enable-libilbc –enable-libmodplug –enable-libmp3lame –enable-libopencor
  e-amrnb –enable-libopencore-amrwb –enable-libopenjpeg –enable-libopus –enable-librtmp –enable-libschroedinger –enable-libsoxr –enable-libspeex –enable-libtheora –enable-libtwolame –en
  able-libvidstab –enable-libvo-aacenc –enable-libvo-amrwbenc –enable-libvorbis –enable-libvpx –enable-libwavpack –enable-libwebp –enable-libx264 –enable-libx265 –enable-libxavs –enable
  -libxvid –enable-lzma –enable-decklink –enable-zlib
  libavutil 54. 23.101 / 54. 23.101
  libavcodec 56. 35.101 / 56. 35.101
  libavformat 56. 31.100 / 56. 31.100
  libavdevice 56. 4.100 / 56. 4.100
  libavfilter 5. 14.100 / 5. 14.100
  libswscale 3. 1.101 / 3. 1.101
  libswresample 1. 1.100 / 1. 1.100
  libpostproc 53. 3.100 / 53. 3.100
  Guessed Channel Layout for Input Stream #0.1 : stereo
  Input #0, mxf, from ‘input file name.MXF’:
  Metadata:
  uid : adab4424-2f25-4dc7-92ff-29bd000b0000
  generation_uid : adab4424-2f25-4dc7-92ff-29bd000b0001
  company_name : FFmpeg
  product_name : OP1a Muxer
  product_version : 54.63.104
  product_uid : adab4424-2f25-4dc7-92ff-29bd000b0002
  modification_date: 0000-01-01 00:00:00
  material_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE000
  timecode : 00:00:00;00
  Duration: 01:00:00.03, start: 0.000000, bitrate: 4592 kb/s
  Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, unknown/bt709/bt709), 1920×1080 [SAR 1:1 DAR 16:9], max. 35000 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 59.94 tbc
  Metadata:
  file_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE001
  Stream #0:1: Audio: pcm_s24le, 48000 Hz, 2 channels, s32 (24 bit), 2304 kb/s
  Metadata:
  file_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE001
  [mpeg2video @ 0000000004edd140] Warning vbv_delay will be set to 0xFFFF (=VBR) as the specified vbv buffer is too large for the given bitrate!
  Output #0, mxf, to ‘iFrame Only output file name.MXF’:
  Metadata:
  uid : adab4424-2f25-4dc7-92ff-29bd000b0000
  generation_uid : adab4424-2f25-4dc7-92ff-29bd000b0001
  company_name : FFmpeg
  product_name : OP1a Muxer
  product_version : 54.63.104
  product_uid : adab4424-2f25-4dc7-92ff-29bd000b0002
  modification_date: 0000-01-01 00:00:00
  material_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE000
  timecode : 00:00:00;00
  encoder : Lavf56.31.100
  Stream #0:0: Video: mpeg2video (xd5c / 0x63356478), yuv420p, 1920×1080 [SAR 1:1 DAR 16:9], q=1-31, 35000 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
  Metadata:
  file_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE001
  encoder : Lavc56.35.101 mpeg2video
  Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16 (24 bit), 1536 kb/s
  Metadata:
  file_package_umid: 0x060A2B340101010501010D0013E00EE4529471344CE00EE400529471344CE001
  encoder : Lavc56.35.101 pcm_s16le
  Stream mapping:
  Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg2video (native))
  Stream #0:1 -> #0:1 (pcm_s24le (native) -> pcm_s16le (native))
  Press [q] to stop, [?] for help
  [mxf @ 0000000002d98440] -d10_channelcount requires MXF D-10 and will be ignored
  frame= 615 fps=313 q=0.8 Lsize= 91196kB time=00:00:20.52 bitrate=36406.4kbits/s
  video:86605kB audio:3848kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.822079%[/code]

  then used the iFrame only file as input file and the command below to cut a chunk of it.

  [code]ffmpeg -ss 0.2002 -i “iFrame Only output file name.MXF” -c:v copy -t [b]19.9533[/b] -an -f MXF -y “iFrame Only Video_1.MXF”
  [/code]

  the log of the command is:

  [code]ffmpeg version N-71737-gb410c69 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.2 (GCC)
  configuration: –enable-gpl –enable-version3 –disable-w32threads –enable-avisynth –enable-bzlib –enable-fontconfig –enable-frei0r –enable-gnutls –enable-iconv –enable-libass –enable
  -libbluray –enable-libbs2b –enable-libcaca –enable-libdcadec –enable-libfreetype –enable-libgme –enable-libgsm –enable-libilbc –enable-libmodplug –enable-libmp3lame –enable-libopencor
  e-amrnb –enable-libopencore-amrwb –enable-libopenjpeg –enable-libopus –enable-librtmp –enable-libschroedinger –enable-libsoxr –enable-libspeex –enable-libtheora –enable-libtwolame –en
  able-libvidstab –enable-libvo-aacenc –enable-libvo-amrwbenc –enable-libvorbis –enable-libvpx –enable-libwavpack –enable-libwebp –enable-libx264 –enable-libx265 –enable-libxavs –enable
  -libxvid –enable-lzma –enable-decklink –enable-zlib
  libavutil 54. 23.101 / 54. 23.101
  libavcodec 56. 35.101 / 56. 35.101
  libavformat 56. 31.100 / 56. 31.100
  libavdevice 56. 4.100 / 56. 4.100
  libavfilter 5. 14.100 / 5. 14.100
  libswscale 3. 1.101 / 3. 1.101
  libswresample 1. 1.100 / 1. 1.100
  libpostproc 53. 3.100 / 53. 3.100
  Guessed Channel Layout for Input Stream #0.1 : stereo
  Input #0, mxf, from ‘iFrame Only output file name.MXF’:
  Metadata:
  uid : adab4424-2f25-4dc7-92ff-29bd000c0000
  generation_uid : adab4424-2f25-4dc7-92ff-29bd000c0001
  company_name : FFmpeg
  product_name : OP1a Muxer
  product_version : 56.31.100
  product_uid : adab4424-2f25-4dc7-92ff-29bd000c0002
  modification_date: 0000-01-01 00:00:00
  material_package_umid: 0x060A2B340101010501010D001346374B529471349946374B0052947134994600
  timecode : 00:00:00;00
  Duration: 00:00:20.52, start: 0.000000, bitrate: 36406 kb/s
  Stream #0:0: Video: mpeg2video (Main), yuv420p(tv), 1920×1080 [SAR 1:1 DAR 16:9], max. 35000 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 59.94 tbc
  Metadata:
  file_package_umid: 0x060A2B340101010501010D001346374B529471349946374B0052947134994601
  Stream #0:1: Audio: pcm_s16le, 48000 Hz, 2 channels, s16, 1536 kb/s
  Metadata:
  file_package_umid: 0x060A2B340101010501010D001346374B529471349946374B0052947134994601
  Output #0, mxf, to ‘iFrame Only Video_1.MXF’:
  Metadata:
  uid : adab4424-2f25-4dc7-92ff-29bd000c0000
  generation_uid : adab4424-2f25-4dc7-92ff-29bd000c0001
  company_name : FFmpeg
  product_name : OP1a Muxer
  product_version : 56.31.100
  product_uid : adab4424-2f25-4dc7-92ff-29bd000c0002
  modification_date: 0000-01-01 00:00:00
  material_package_umid: 0x060A2B340101010501010D001346374B529471349946374B0052947134994600
  timecode : 00:00:00;00
  encoder : Lavf56.31.100
  Stream #0:0: Video: mpeg2video, yuv420p, 1920×1080 [SAR 1:1 DAR 16:9], q=2-31, max. 35000 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc
  Metadata:
  file_package_umid: 0x060A2B340101010501010D001346374B529471349946374B0052947134994601
  Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Press [q] to stop, [?] for help
  frame= 600 fps=0.0 q=-1.0 Lsize= 85564kB [b]time=00:00:19.98[/b] bitrate=35070.5kbits/s
  video:84986kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.679815%
  [/code]

  as you can compare the command and log, value of -t in command is 19.9533 and time in log is 19.98. (the log shows that the output is one Frame longer). but when I check the specs of output by MediaInfo it show that the duration is 20.020 (two frames longer than the command).

  any comments or suggestion on why it happens?

  thanks

  Mohammad Torabi replied 11 years, 2 months ago 1 Member · 0 Replies
• 0 Replies

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