What's the difference between "-filter_complex" and "-vf" when only one
filter is used? Specially, when the "scale" filter is used.
I assumed the results would be the same, but discovered the "-vf" version
creates an mpeg2 file almost 80M larger for my ~600M input test file.
$ ls -lGg TEST.mkv TEST-fc.mpg TEST-vf.mpg
-rw-r--r--. 1 620992404 Nov 17 20:58 TEST.mkv
-rw-r--r--. 1 578318336 Nov 17 21:02 TEST-fc.mpg
-rw-r--r--. 1 660838400 Nov 17 21:06 TEST-vf.mpg
But the video specs appear to be the same for both output files:
$ for i in TEST-fc.mpg TEST-vf.mpg; do ffmpeg -i $i 2>&1 | egrep
'Input|Stream'; done
Input #0, mpeg, from 'TEST-fc.mpg':
Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, progressive),
1711x720 [SAR 1:1 DAR 1711:720], 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc
Input #0, mpeg, from 'TEST-vf.mpg':
Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, progressive),
1711x720 [SAR 1:1 DAR 1711:720], 23.98 fps, 23.98 tbr, 90k tbn, 47.95 tbc
The TEST.mkv input file is only 10 mins of the video stream from the
original 2hr file. The difference in size for the original (~9G) file is
about 1G (7.4G for "-filter_complex" vs 8.4G for "-vf).
Here's complete output for both 10 min TEST output files:
$ ffmpeg -i TEST.mkv -codec:v mpeg2video -b:v 16384k -bufsize 4096k -maxrate
30000k -filter_complex 'scale=-1:720' -f vob TEST-fc.mpg
ffmpeg version N-89089-g80bb81a Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.9.2 (GCC) 20150212 (Red Hat 4.9.2-6)
configuration: --enable-gpl --enable-version3 --enable-nonfree
--enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame
--enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx
--enable-libx264 --enable-libx265 --enable-libcdio --enable-libbluray
--enable-openssl --disable-ffplay --disable-ffserver
libavutil 56. 0.100 / 56. 0.100
libavcodec 58. 3.102 / 58. 3.102
libavformat 58. 2.100 / 58. 2.100
libavdevice 58. 0.100 / 58. 0.100
libavfilter 7. 0.101 / 7. 0.101
libswscale 5. 0.101 / 5. 0.101
libswresample 3. 0.101 / 3. 0.101
libpostproc 55. 0.100 / 55. 0.100
Input #0, matroska,webm, from 'TEST.mkv':
Metadata:
ENCODER : Lavf58.2.100
Duration: 00:10:00.23, start: 0.000000, bitrate: 8276 kb/s
Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x808, SAR 1:1
DAR 240:101, 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Metadata:
DURATION : 00:10:00.225000000
Stream mapping:
Stream #0:0 (h264) -> scale
scale -> Stream #0:0 (mpeg2video)
Press [q] to stop, [?] for help
Output #0, vob, to 'TEST-fc.mpg':
Metadata:
encoder : Lavf58.2.100
Stream #0:0: Video: mpeg2video (Main), yuv420p, 1711x720 [SAR
172800:172811 DAR 240:101], q=2-31, 16384 kb/s, 23.98 fps, 90k tbn, 23.98 tbc
(default)
Metadata:
encoder : Lavc58.3.102 mpeg2video
Side data:
cpb: bitrate max/min/avg: 30000000/0/16384000 buffer size: 4096000
vbv_delay: -1
frame=14391 fps= 74 q=2.0 Lsize= 564764kB time=00:10:00.14
bitrate=7709.1kbits/s dup=3 drop=0 speed=3.08x
video:557904kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 1.229569%
$ ffmpeg -i TEST.mkv -codec:v mpeg2video -b:v 16384k -bufsize 4096k -maxrate
30000k -vf 'scale=-1:720' -f vob TEST-vf.mpg
ffmpeg version N-89089-g80bb81a Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.9.2 (GCC) 20150212 (Red Hat 4.9.2-6)
configuration: --enable-gpl --enable-version3 --enable-nonfree
--enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame
--enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx
--enable-libx264 --enable-libx265 --enable-libcdio --enable-libbluray
--enable-openssl --disable-ffplay --disable-ffserver
libavutil 56. 0.100 / 56. 0.100
libavcodec 58. 3.102 / 58. 3.102
libavformat 58. 2.100 / 58. 2.100
libavdevice 58. 0.100 / 58. 0.100
libavfilter 7. 0.101 / 7. 0.101
libswscale 5. 0.101 / 5. 0.101
libswresample 3. 0.101 / 3. 0.101
libpostproc 55. 0.100 / 55. 0.100
Input #0, matroska,webm, from 'TEST.mkv':
Metadata:
ENCODER : Lavf58.2.100
Duration: 00:10:00.23, start: 0.000000, bitrate: 8276 kb/s
Stream #0:0: Video: h264 (High), yuv420p(progressive), 1920x808, SAR 1:1
DAR 240:101, 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Metadata:
DURATION : 00:10:00.225000000
Stream mapping:
Stream #0:0 -> #0:0 (h264 (native) -> mpeg2video (native))
Press [q] to stop, [?] for help
Output #0, vob, to 'TEST-vf.mpg':
Metadata:
encoder : Lavf58.2.100
Stream #0:0: Video: mpeg2video (Main), yuv420p, 1711x720 [SAR
172800:172811 DAR 240:101], q=2-31, 16384 kb/s, 23.98 fps, 90k tbn, 23.98 tbc
(default)
Metadata:
DURATION : 00:10:00.225000000
encoder : Lavc58.3.102 mpeg2video
Side data:
cpb: bitrate max/min/avg: 30000000/0/16384000 buffer size: 4096000
vbv_delay: -1
frame=14391 fps= 68 q=2.0 Lsize= 645350kB time=00:10:00.14
bitrate=8809.1kbits/s dup=3 drop=0 speed=2.83x
video:637531kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 1.226453%
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