[FFmpeg-trac] #3137(undetermined:new): bitrate artefacts with libvpx

FFmpeg trac at avcodec.org
Thu Nov 14 17:18:53 CET 2013


#3137: bitrate artefacts with libvpx
-------------------------------------+-------------------------------------
               Reporter:  ubitux     |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:             |  undetermined
  unspecified                        |               Keywords:  libvpx
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 When encoding a webm/vp8 with default settings, some weird artefacts
 appear at regular intervals.

 {{{
 ☭ ./ffmpeg -loop 1 -i tests/lena.pnm -vf 'scale=2*iw:2*ih' -t 20 -y
 out.webm
 ffmpeg version N-58093-g54af7ce Copyright (c) 2000-2013 the FFmpeg
 developers
   built on Nov 14 2013 19:11:51 with gcc 4.8.2 (GCC)
   configuration: --enable-gpl --enable-libx264 --enable-libmp3lame
 --enable-x11grab --enable-libvorbis --samples=/home/ux/fate-samples
 --enable-libfreetype --enable-libvpx --cpu=native --cc='ccache cc'
   libavutil      52. 53.100 / 52. 53.100
   libavcodec     55. 43.100 / 55. 43.100
   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, image2, from 'tests/lena.pnm':
   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: ppm, rgb24, 256x256, 25 fps, 25 tbr, 25 tbn, 25
 tbc
 [libvpx @ 0x181a160] v1.2.0
 Output #0, webm, to 'out.webm':
   Metadata:
     encoder         : Lavf55.21.100
     Stream #0:0: Video: vp8 (libvpx), yuv420p, 512x512, q=-1--1, 200 kb/s,
 1k tbn, 25 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (ppm -> libvpx)
 Press [q] to stop, [?] for help
 frame=  500 fps=149 q=0.0 Lsize=     434kB time=00:00:20.00 bitrate=
 177.9kbits/s
 video:431kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 0.898042%
 }}}

 Then play {{{out.webm}}}: at t=5s, t=10s and t=15s, one single frame gets
 "flashy" (just like if bitrate was wrong/very-low for those frames). It's
 less visible if bitrate is raised but still visible (try adding {{{-b:v
 1M}}}).

 It's probably some kind of rate control bug in libvpx, but maybe something
 is wrong in the wrapper (I don't have time to dig this issue) so I'm
 opening a ticket.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3137>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker


More information about the FFmpeg-trac mailing list