[FFmpeg-trac] #5903(avformat:new): remuxing to Matroska has inaccurate (slightly) display aspect ratio
FFmpeg
trac at avcodec.org
Fri Oct 21 23:47:18 EEST 2016
#5903: remuxing to Matroska has inaccurate (slightly) display aspect ratio
--------------------------------------+----------------------------------
Reporter: dericed | Owner:
Type: defect | Status: new
Priority: normal | Component: avformat
Version: git-master | Keywords: matroska
Blocked By: | Blocking:
Reproduced by developer: 0 | Analyzed by developer: 0
--------------------------------------+----------------------------------
Summary of the bug:
To demonstate I'm using a reference file in mov created via:
{{{
ffmpeg -f lavfi -i testsrc=s=720x480 -frames:v 1 -aspect 15/11
s720x480_dar15x11.mov
}}}
Then remux to mkv via:
{{{
drice:scripts drice$ ffmpeg -i s720x480_dar15x11.mov -c copy
s720x480_dar15x11.mkv
ffmpeg version git-2016-10-21-5db3c94 Copyright (c) 2000-2016 the FFmpeg
developers
built with Apple LLVM version 8.0.0 (clang-800.0.38)
configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD-5db3c94 --enable-
shared --enable-pthreads --enable-gpl --enable-version3 --enable-
hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-
ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-
libxvid --enable-libfreetype --enable-libass --disable-lzma --enable-
libopenjpeg --disable-decoder=jpeg2000 --extra-
cflags=-I/usr/local/Cellar/openjpeg/2.1.2/include/openjpeg-2.1 --enable-
vda
libavutil 55. 32.100 / 55. 32.100
libavcodec 57. 63.103 / 57. 63.103
libavformat 57. 52.100 / 57. 52.100
libavdevice 57. 0.103 / 57. 0.103
libavfilter 6. 64.100 / 6. 64.100
libavresample 3. 0. 0 / 3. 0. 0
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 2.100 / 2. 2.100
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 's720x480_dar15x11.mov':
Metadata:
major_brand : qt
minor_version : 512
compatible_brands: qt
encoder : Lavf57.52.100
Duration: 00:00:00.04, start: 0.000000, bitrate: 1039 kb/s
Stream #0:0(eng): Video: h264 (High 4:4:4 Predictive) (avc1 /
0x31637661), yuv444p, 720x480 [SAR 10:11 DAR 15:11], 869 kb/s, 25 fps, 25
tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : DataHandler
encoder : Lavc57.63.103 libx264
Output #0, matroska, to 's720x480_dar15x11.mkv':
Metadata:
major_brand : qt
minor_version : 512
compatible_brands: qt
encoder : Lavf57.52.100
Stream #0:0(eng): Video: h264 (High 4:4:4 Predictive) (avc1 /
0x31637661), yuv444p, 720x480 [SAR 10:11 DAR 15:11], q=2-31, 869 kb/s, 25
fps, 25 tbr, 1k tbn, 12800 tbc (default)
Metadata:
handler_name : DataHandler
encoder : Lavc57.63.103 libx264
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 1 fps=0.0 q=-1.0 Lsize= 5kB time=00:00:00.00
bitrate=42232.0kbits/s speed=3.37x
video:4kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 21.412144%
}}}
In the resulting MKV file it has these values in the Video Element:
{{{
PixelWidth=720
PixelHeight=480
DisplayWidth=655
DisplayHeight=480
DisplayUnit={unstored, thus defaults to '0' which is 'pixels'}
}}}
This creates a minor DAR change since:
mov's DAR is (720/480)*(10/11) ~= 1.3636363636
mkv's DAR is 655/480 ~= 1.3645833333
If the file was remuxed with these values:
{{{
PixelWidth=720
PixelHeight=480
DisplayWidth=15
DisplayHeight=11
DisplayUnit=3 (3 means 'Display Aspect Ratio')
}}}
then the mov and the mkv would have an exact match for DAR.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/5903>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
More information about the FFmpeg-trac
mailing list