[FFmpeg-user] mpeg2 bufsize question

[Dave P]

Hello list,

How do you calculate bufsize?  No matter what value I choose, I get
underflow errors and my qscale value goes up:

c:\ffmpeg_x64\bin>ffmpeg -i C:\temp\vids\155064\155064.mov -c:v mpeg2video -q:v
2 -bufsize 1M -vf yadif=0,scale=1920:1080 -aspect 16:9 -c:a mp2 -b:a 384k -y C:\
temp\vids\155064\155064-q2.mpg
ffmpeg version N-36635-gceb0dd9 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jan  9 2012 17:45:55 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib
  libavutil      51. 34.100 / 51. 34.100
  libavcodec     53. 54.100 / 53. 54.100
  libavformat    53. 29.100 / 53. 29.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 58.100 /  2. 58.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  6.100 /  0.  6.100
  libpostproc    51.  2.100 / 51.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\temp\vids\155064\155064.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2011-10-08 23:30:10
  Duration: 01:36:48.67, start: 0.000000, bitrate: 26534 kb/s
    Stream #0:0(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s1
6, 1536 kb/s
    Metadata:
      creation_time   : 2011-10-08 23:30:10
      handler_name    : ?Apple Alias Data Handler
    Stream #0:1(eng): Video: mpeg2video (Main) (hdv2 / 0x32766468), yuv420p, 144
0x1080 [SAR 4:3 DAR 16:9], 25000 kb/s, 29.97 fps, 29.97 tbr, 2997 tbn, 59.94 tbc

    Metadata:
      creation_time   : 2011-10-08 23:30:10
      handler_name    : ?Apple Alias Data Handler
[buffer @ 00000000041C2D40] w:1440 h:1080 pixfmt:yuv420p tb:1/1000000 sar:4/3 sw
s_param:
[yadif @ 0000000001C5CBB0] mode:0 parity:-1 auto_enable:0
[scale @ 0000000001C5CCC0] w:1440 h:1080 fmt:yuv420p -> w:1920 h:1080 fmt:yuv420
p flags:0x4
Output #0, mpeg, to 'C:\temp\vids\155064\155064-q2.mpg':
  Metadata:
    major_brand     : qt
    minor_version   : 537199360
    compatible_brands: qt
    creation_time   : 2011-10-08 23:30:10
    encoder         : Lavf53.29.100
    Stream #0:0(eng): Video: mpeg2video, yuv420p, 1920x1080 [SAR 1:1 DAR 16:9],
q=2-31, 200 kb/s, 90k tbn, 29.97 tbc
    Metadata:
      creation_time   : 2011-10-08 23:30:10
      handler_name    : ?Apple Alias Data Handler
    Stream #0:1(eng): Audio: mp2, 48000 Hz, stereo, s16, 384 kb/s
    Metadata:
      creation_time   : 2011-10-08 23:30:10
      handler_name    : ?Apple Alias Data Handler
Stream mapping:
  Stream #0:1 -> #0:0 (mpeg2video -> mpeg2video)
  Stream #0:0 -> #0:1 (pcm_s16le -> mp2)
Press [q] to stop, [?] for help
[mpeg2video @ 0000000001D4DE60] warning: first frame is no keyframe
    Last message repeated 1 times
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 6 times
frame=    7 fps=  0 q=31.0 size=      36kB time=00:00:00.20 bitrate=1473.1kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   14 fps= 12 q=31.0 size=      74kB time=00:00:00.43 bitrate=1397.5kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   21 fps= 12 q=31.0 size=      80kB time=00:00:00.66 bitrate= 982.1kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   28 fps= 12 q=31.0 size=     118kB time=00:00:00.90 bitrate=1073.0kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 4 times
frame=   34 fps= 12 q=31.0 size=     134kB time=00:00:01.10 bitrate= 996.9kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   41 fps= 12 q=31.0 size=     182kB time=00:00:01.33 bitrate=1117.1kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   48 fps= 12 q=31.0 size=     194kB time=00:00:01.56 bitrate=1013.4kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow
    Last message repeated 5 times
frame=   55 fps= 12 q=31.0 size=     240kB time=00:00:01.80 bitrate=1091.2kbits/
rc buffer underflow
[mpeg2video @ 0000000001CC2C60] rc buffer underflow

Thanks,

dp