[FFmpeg-trac] #6574(swscale:new): ffmpeg butchers video quality when downscaling
FFmpeg
trac at avcodec.org
Tue Aug 8 13:45:41 EEST 2017
#6574: ffmpeg butchers video quality when downscaling
----------------------------------+-----------------------------------
Reporter: birdie | Owner:
Type: defect | Status: new
Priority: critical | Component: swscale
Version: 3.2.4 | Resolution:
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
----------------------------------+-----------------------------------
Comment (by birdie):
I've tried ffmpeg from git - the result is the same:
{{{
ffmpeg -i source.mkv -vf scale=768x342 -sws_flags spline -c:v libx264
-preset veryslow -x264opts keyint=230:min-keyint=23:bframes=16 -crf 0
-tune film result.mkv
ffmpeg version N-86925-g4ff94558f2 Copyright (c) 2000-2017 the FFmpeg
developers
built with gcc 6.4.0 (Debian 6.4.0-2) 20170724
configuration: --enable-gpl --enable-version3 --enable-static --disable-
debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio
--cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-
gray --enable-libass --enable-libfreetype --enable-libfribidi --enable-
libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-
libopenjpeg --enable-libopus --enable-librtmp --enable-libsoxr --enable-
libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc
--enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264
--enable-libx265 --enable-libxvid --enable-libzimg
libavutil 55. 69.100 / 55. 69.100
libavcodec 57.102.100 / 57.102.100
libavformat 57. 76.100 / 57. 76.100
libavdevice 57. 7.100 / 57. 7.100
libavfilter 6. 96.100 / 6. 96.100
libswscale 4. 7.101 / 4. 7.101
libswresample 2. 8.100 / 2. 8.100
libpostproc 54. 6.100 / 54. 6.100
Input #0, matroska,webm, from 'source.mkv':
Metadata:
ENCODER : Lavf57.56.100
Duration: 00:00:14.43, start: 0.000000, bitrate: 5636 kb/s
Chapter #0:0: start 0.000000, end 179.000000
Chapter #0:1: start 179.000000, end 998.000000
Chapter #0:2: start 998.000000, end 1598.000000
Chapter #0:3: start 1598.000000, end 2043.000000
Chapter #0:4: start 2043.000000, end 2614.000000
Chapter #0:5: start 2614.000000, end 3387.000000
Chapter #0:6: start 3387.000000, end 4007.000000
Chapter #0:7: start 4007.000000, end 4729.000000
Chapter #0:8: start 4729.000000, end 5163.504000
Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x800 [SAR
1:1 DAR 12:5], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Metadata:
DURATION : 00:00:14.431000000
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x4817540] using SAR=171/160
[libx264 @ 0x4817540] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
AVX
[libx264 @ 0x4817540] profile High 4:4:4 Predictive, level 3.1, 4:2:0
8-bit
[libx264 @ 0x4817540] 264 - core 152 r19 ba24899 - H.264/MPEG-4 AVC codec
- Copyleft 2003-2017 - http://www.videolan.org/x264.html - options:
cabac=1 ref=16 deblock=1:-1:-1 analyse=0x1:0x131 me=umh subme=9 psy=0
mixed_ref=1 me_range=24 chroma_me=1 trellis=0 8x8dct=1 cqm=0
deadzone=21,11 fast_pskip=0 chroma_qp_offset=0 threads=6
lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0
bluray_compat=0 constrained_intra=0 bframes=0 weightp=2 keyint=230
keyint_min=23 scenecut=40 intra_refresh=0 rc=cqp mbtree=0 qp=0
Output #0, matroska, to 'result.mkv':
Metadata:
encoder : Lavf57.76.100
Chapter #0:0: start 0.000000, end 179.000000
Chapter #0:1: start 179.000000, end 998.000000
Chapter #0:2: start 998.000000, end 1598.000000
Chapter #0:3: start 1598.000000, end 2043.000000
Chapter #0:4: start 2043.000000, end 2614.000000
Chapter #0:5: start 2614.000000, end 3387.000000
Chapter #0:6: start 3387.000000, end 4007.000000
Chapter #0:7: start 4007.000000, end 4729.000000
Chapter #0:8: start 4729.000000, end 5163.504000
Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv420p,
768x342 [SAR 171:160 DAR 12:5], q=-1--1, 23.98 fps, 1k tbn, 23.98 tbc
(default)
Metadata:
DURATION : 00:00:14.431000000
encoder : Lavc57.102.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame= 343 fps= 30 q=-1.0 Lsize= 27649kB time=00:00:14.39
bitrate=15740.4kbits/s speed=1.24x
video:27645kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.014695%
[libx264 @ 0x4817540] frame I:5 Avg QP: 0.00 size:152679
[libx264 @ 0x4817540] frame P:338 Avg QP: 0.00 size: 81494
[libx264 @ 0x4817540] mb I I16..4: 22.0% 0.0% 78.0%
[libx264 @ 0x4817540] mb P I16..4: 6.6% 0.0% 3.6% P16..4: 49.6% 15.2%
21.5% 1.8% 1.6% skip: 0.0%
[libx264 @ 0x4817540] 8x8 transform intra:0.0% inter:66.4%
[libx264 @ 0x4817540] coded y,uvDC,uvAC intra: 92.9% 99.8% 99.8% inter:
99.7% 99.7% 99.6%
[libx264 @ 0x4817540] i16 v,h,dc,p: 67% 31% 2% 0%
[libx264 @ 0x4817540] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 59% 24% 4% 2% 3%
3% 2% 1% 1%
[libx264 @ 0x4817540] i8c dc,h,v,p: 9% 26% 63% 2%
[libx264 @ 0x4817540] Weighted P-Frames: Y:0.9% UV:0.0%
[libx264 @ 0x4817540] ref P L0: 74.9% 8.6% 10.8% 2.3% 1.4% 0.6% 0.4%
0.2% 0.2% 0.2% 0.1% 0.1% 0.0% 0.0% 0.0% 0.0%
[libx264 @ 0x4817540] kb/s:15602.79
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/6574#comment:2>
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