[FFmpeg-devel] parameter ranges bug / minrate q

tripp eliared
Thu Jul 17 18:29:16 CEST 2008


1. i'd like to ask the exact meaning of this:
[mpeg4 @ 00AD0900]Warning min_rate > 0 but min_rate != max_rate 
isn't recommended!

i asked over a week ago on ffmpeg-user.
at first i'd thought i didn't pad the bitsream 
like other encoders, with a minrate setting,
but it seems to do so,

so i assume that there's the recommendation because,
setting -minrate != -maxrate ratecontrol is unable to meet target bitrate?
and currently -minrate is only useful in setting cbr encodes,
with minrate=maxrate?
if so is it to change?
a word in the docs would be nice.

2. values of 0 for:

return errors like so:
ffmpeg143 -i input.avi -b 700k -qcomp 0 -an -y out.mp4
FFmpeg version SVN-r14236, Copyright (c) 2000-2008 Fabrice Bellard, et al.
  configuration: --enable-memalign-hack --enable-postproc --enable-swscale --ena
ble-gpl --enable-libfaac --enable-libfaad --enable-libgsm --enable-libmp3lame --
enable-libvorbis --enable-libtheora --enable-libx264 --enable-libxvid --disable-
ffserver --disable-vhook --enable-avisynth --enable-pthreads
  libavutil version: 49.7.0
  libavcodec version: 51.60.0
  libavformat version: 52.17.0
  libavdevice version: 52.0.0
  built on Jul 15 2008 19:35:58, gcc: 4.2.4 (TDM-1 for MinGW)

Seems stream 0 codec frame rate differs from container frame rate: 23.98 (65535/
2733) -> 23.98 (24000/1001)
Input #0, avi, from 'input.avi':
  Duration: 00:00:41.71, start: 0.000000, bitrate: 689 kb/s
    Stream #0.0: Video: mpeg4, yuv420p, 624x352 [PAR 1:1 DAR 39:22], 23.98 tb(r)

    Stream #0.1: Audio: mp3, 44100 Hz, stereo, 112 kb/s
Value 0.000000 for parameter 'qcomp' out of range.
Value 0.000000 for parameter 'qcomp' out of range.
Value 0.000000 for parameter 'qcomp' out of range.
ffmpeg143: unrecognized option '-qcomp'

for all of the above,
0 seems like a perfeclty valid value.
certainly an offset, within all logic can always be zero.

-qblur 0 , should disable 

it's stated in at least a few docs that -qcomp 0 is valid,
that it sets cbr encoding as opposed to -qcomp 1 to set constant quant
encoding (assuming default rc_eq)

3. speaking of,
setting -rc_eq "1" does not deliver a cbr encode
nor does -rc_eq "tex" do the opposite from what i gather.

if you care to pm me with any answers, i'll take em.



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