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cutting iFrame only media

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Mohammad Torabi
cutting iFrame only media
on Apr 28, 2015 at 5:13:45 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), 1920x1080 [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, 1920x1080 [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), 1920x1080 [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, 1920x1080 [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


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