#2452: decoding yuv420p to rgb shifts luminance down
-------------------------------------+-------------------------------------
Reporter: burek | Owner:
Type: defect | Status: new
Priority: normal | Component:
Version: unspecified | undetermined
Keywords: | Resolution:
Blocking: | Blocked By:
Analyzed by developer: 0 | Reproduced by developer: 0
-------------------------------------+-------------------------------------
Comment (by glopes):
Thanks for asking, actually! I just tried with the latest build (ffmpeg
version N-55159-gf118b41) and it turns out now it's not even possible to
get the correct luminance values by using the first command line!!
I don't know what changed about pix_fmt gray decoding from yuv420p, but
now things are even worse as I have currently no way of recovering the
correct luminance from my recorded videos... data loss is now a serious
possibility...
Last known working version is ffmpeg version N-51639-g7775992.
Here's the output from the two commands now:
gray pix_fmt:
{{{
ffmpeg -ss 0.5 -i video.avi -vframes 1 -t 1 -s 1280x680 -pix_fmt gray
gray.bmp
}}}
{{{
ffmpeg version N-55159-gf118b41 Copyright (c) 2000-2013 the FFmpeg
developers
built on Aug 1 2013 18:08:30 with gcc 4.7.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-
libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame
--ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr
--enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-
libvo-
amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-
libxavs --
enable-libxvid --enable-zlib
libavutil 52. 40.100 / 52. 40.100
libavcodec 55. 19.100 / 55. 19.100
libavformat 55. 12.102 / 55. 12.102
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 82.100 / 3. 82.100
libswscale 2. 4.100 / 2. 4.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, avi, from 'video.avi':
Metadata:
encoder : Lavf53.22.0
Duration: 00:00:13.59, start: 0.000000, bitrate: 5596 kb/s
Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46),
yuv420p, 128
0x680 [SAR 1:1 DAR 32:17], 120 fps, 120 tbr, 120 tbn, 120 tbc
File 'gray.bmp' already exists. Overwrite ? [y/N] y
Output #0, image2, to 'gray.bmp':
Metadata:
encoder : Lavf55.12.102
Stream #0:0: Video: bmp, gray, 1280x680 [SAR 1:1 DAR 32:17], q=2-31,
200 kb/
s, 90k tbn, 120 tbc
Stream mapping:
Stream #0:0 -> #0:0 (mpeg4 -> bmp)
Press [q] to stop, [?] for help
frame= 1 fps=0.0 q=-1.0 Lsize=N/A time=00:00:00.00 bitrate=N/A
video:851kB audio:0kB subtitle:0 global headers:0kB muxing overhead
-100.002524%
}}}
bgr24 pix_fmt:
{{{
ffmpeg -ss 0.5 -i video.avi -vframes 1 -t 1 -s 1280x680 -pix_fmt bgr24
rgb.bmp
}}}
{{{
ffmpeg version N-55159-gf118b41 Copyright (c) 2000-2013 the FFmpeg
developers
built on Aug 1 2013 18:08:30 with gcc 4.7.3 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls
--enab
le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-
libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame
--ena
ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-l
ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr
--enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-
libvo-
amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-
libxavs --
enable-libxvid --enable-zlib
libavutil 52. 40.100 / 52. 40.100
libavcodec 55. 19.100 / 55. 19.100
libavformat 55. 12.102 / 55. 12.102
libavdevice 55. 3.100 / 55. 3.100
libavfilter 3. 82.100 / 3. 82.100
libswscale 2. 4.100 / 2. 4.100
libswresample 0. 17.103 / 0. 17.103
libpostproc 52. 3.100 / 52. 3.100
Input #0, avi, from 'video.avi':
Metadata:
encoder : Lavf53.22.0
Duration: 00:00:13.59, start: 0.000000, bitrate: 5596 kb/s
Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46),
yuv420p, 128
0x680 [SAR 1:1 DAR 32:17], 120 fps, 120 tbr, 120 tbn, 120 tbc
File 'rgb.bmp' already exists. Overwrite ? [y/N] y
Output #0, image2, to 'rgb.bmp':
Metadata:
encoder : Lavf55.12.102
Stream #0:0: Video: bmp, bgr24, 1280x680 [SAR 1:1 DAR 32:17], q=2-31,
200 kb
/s, 90k tbn, 120 tbc
Stream mapping:
Stream #0:0 -> #0:0 (mpeg4 -> bmp)
Press [q] to stop, [?] for help
frame= 1 fps=0.0 q=-1.0 Lsize=N/A time=00:00:00.00 bitrate=N/A
video:2550kB audio:0kB subtitle:0 global headers:0kB muxing overhead
-100.000843
%
}}}
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2452#comment:5>
FFmpeg <http://ffmpeg.org>
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