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FFMPEG ProRes 422 > How to set custom bitrate?

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Michal Shipman
FFMPEG ProRes 422 > How to set custom bitrate?
on Nov 7, 2013 at 12:49:21 am

Hi there, I'm trying to export a trailer for a distributor and they said the bitrate was to small. It had a bitrate of 120mbs and needed to be 160mbs. I've a lot of different combinations and I can't seem to get FFMPEG to use a fixed bitrate.

Here's the string I'm using.

J:>Ffmpeg -i trailer.avs -r 23.976 -codec:v prores -b:v 2000000k -profile:v 2 -codec:a pcm_s16le -filter_complex asetnsamples=n=16384:p=0 trailer6.1920x1080p.p
rores422.mov

No matter what I put in for the -b:v command, it seems to default to the normal 200kbs.

Here's what the console says:

ffmpeg version N-57906-gbd75651 Copyright (c) 2000-2013 the FFmpeg developers
built on Nov 4 2013 18:01:33 with gcc 4.8.2 (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-libvidstab --enable-libvo-aa
cenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavp
ack --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
libavutil 52. 51.100 / 52. 51.100
libavcodec 55. 41.100 / 55. 41.100
libavformat 55. 21.100 / 55. 21.100
libavdevice 55. 5.100 / 55. 5.100
libavfilter 3. 90.101 / 3. 90.101
libswscale 2. 5.101 / 2. 5.101
libswresample 0. 17.104 / 0. 17.104
libpostproc 52. 3.100 / 52. 3.100
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, avisynth, from 'trailer.avs':
Duration: 00:01:26.79, start: 0.000000, bitrate: 0 kb/s
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1920x1013, 23.98
fps, 23.98 tbr, 23.98 tbn, 23.98 tbc
Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
File 'trailer6.1920x1080p.prores422.mov' already exists. Overwrite ? [y/N] y
Output #0, mov, to 'trailer6.1920x1080p.prores422.mov':
Metadata:
encoder : Lavf55.21.100
Stream #0:0: Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 15
36 kb/s
Stream #0:1: Video: prores (apcn) (apcn / 0x6E637061), yuv422p10le, 1920x101
3, q=2-31, 2000000 kb/s, 11988 tbn, 23.98 tbc
Stream mapping:
Stream #0:1 (pcm_s16le) -> asetnsamples (graph 0)
asetnsamples (graph 0) -> Stream #0:0 (pcm_s16le)
Stream #0:0 -> #0:1 (rawvideo -> prores)


The only way I've for sure been able to get the desired bitrate was to to change the profile from 2 to 3 which is Proress 422 (HQ).

Any help would be appreciated.

--
Michal Shipman
Editor, Colorist, Director, DVD & Bluray Design
http://www.michalshipman.com
http://www.imdb.com/name/nm2988456/
---------------------------


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Reuben Martin
Re: FFMPEG ProRes 422 > How to set custom bitrate?
on Nov 8, 2013 at 4:17:18 pm

You can't compare the bitrates of ProRes encoded by ffmpeg to the bitrates encoded by Apple software. The ffmpeg implementations are much more efficient than the apple implementation. Basically the DC transforms used by Apple suck.

Bitrate doesn't matter. Quality of encoding matters. FFmpeg is not going to use the full 200 MBit bandwith when the content of the video does not require that much bandwidth to encode.

If you want to ensure the absolute highest quality, ditch the bitrate settings, and set the qscale to 1.

-qscale:v 1


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Reuben Martin
Re: FFMPEG ProRes 422 > How to set custom bitrate?
on Nov 8, 2013 at 4:21:47 pm

Oh, and set the profile to 3.


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