[FFmpeg-trac] #3150(avcodec:open): H.261 encoding: "-cmp rd" ruins image quality

[FFmpeg]

#3150: H.261 encoding: "-cmp rd" ruins image quality
------------------------------------+-----------------------------------
             Reporter:  maikmerten  |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:  h261        |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  0           |
------------------------------------+-----------------------------------
Changes (by cehoyos):

 * keywords:   => h261
 * status:  new => open
 * reproduced:  0 => 1


Comment:

 For future tickets: Please always provide your failing command line
 together with complete, uncut console output. If a problem is reproducible
 with {{{-f lavfi -i testsrc}}} please consider using it since it it may
 make reproducing the whole ticket easier.

 Image quality starts to degrade after 20 seconds, also reproducible with
 -mbd 1 (-mbd 0 looks better).
 {{{
 $ ffmpeg -f lavfi -i testsrc=s=352x288 -vb 256k -cmp rd -t 60 out.h261
 ffmpeg version N-58249-g2974050 Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Nov 18 2013 18:18:50 with gcc 4.7 (SUSE Linux)
   configuration: --enable-gpl
   libavutil      52. 53.100 / 52. 53.100
   libavcodec     55. 43.101 / 55. 43.101
   libavformat    55. 21.100 / 55. 21.100
   libavdevice    55.  5.100 / 55.  5.100
   libavfilter     3. 91.100 /  3. 91.100
   libswscale      2.  5.101 /  2.  5.101
   libswresample   0. 17.104 /  0. 17.104
   libpostproc    52.  3.100 / 52.  3.100
 Input #0, lavfi, from 'testsrc=s=352x288':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 352x288
 [SAR 1:1 DAR 11:9], 25 tbr, 25 tbn, 25 tbc
 Output #0, h261, to 'out.h261':
   Metadata:
     encoder         : Lavf55.21.100
     Stream #0:0: Video: h261, yuv420p, 352x288 [SAR 1:1 DAR 11:9], q=2-31,
 256 kb/s, 90k tbn, 25 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo -> h261)
 Press [q] to stop, [?] for help
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to -127..127
     Last message repeated 16 times
 [h261 @ 0x306e800] warning, clipping 2 dct coefficients to -127..127
     Last message repeated 1 times
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to -127..127
     Last message repeated 4 times
 [h261 @ 0x306e800] warning, clipping 2 dct coefficients to -127..127
     Last message repeated 1 times
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to -127..127
     Last message repeated 5 times
 [h261 @ 0x306e800] warning, clipping 2 dct coefficients to -127..127
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to -127..127
     Last message repeated 12 times
 [h261 @ 0x306e800] warning, clipping 2 dct coefficients to -127..127
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to -127..127
     Last message repeated 76 times
 [h261 @ 0x306e800] warning, clipping 1 dct coefficients to
 -127..127411.3kbits/s
     Last message repeated 47 times
 frame= 1500 fps=606 q=31.0 Lsize=    3090kB time=00:01:00.00 bitrate=
 422.0kbits/s
 video:3090kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 0.000000%
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3150#comment:1>
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