[FFmpeg-trac] #3150(avcodec:new): H.261 encoding: "-cmp rd" ruins image quality
FFmpeg
trac at avcodec.org
Mon Nov 18 17:39:08 CET 2013
#3150: H.261 encoding: "-cmp rd" ruins image quality
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Reporter: maikmerten | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
How to reproduce:
{{{
ffmpeg -i /tmp/test.y4m -f h261 -vb 256k -cmp rd /tmp/test.h261
ffmpeg version N-58246-g7d0e927 Copyright (c) 2000-2013 the FFmpeg
developers
built on Nov 18 2013 17:15:01 with gcc 4.8 (Ubuntu/Linaro
4.8.1-10ubuntu8)
}}}
Test sequence used is
http://media.xiph.org/video/derf/y4m/sign_irene_cif.y4m
Bitrate of the file is very much inflated by specifying the -cmp rd
option, yet picture quality is severely affected by blockyness. Apparently
the encoder is forced into aggressive quantization.
Attached picture shows one representative frame of video output.
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3150>
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