[Ffmpeg-devel] Problems with MPEG quality

[Víctor Paesa]

Hi,

> Hi all,
>
> I'm having some problems with the latest SVN and the quality of mpeg1 and
> mpeg2 video streams it produces when encoding from a stream of images.
>
> This is a recent problem that first surfaced around the middle of October,
> disappeared in a subsequent SVN update and now is back in the latest SVN.
>
> FFmpeg produces a strange pulsating effect where to the eye, the video
> bitrate
> seems to momentarily dip down drastically for a couple of frames and then
> dips back up to the specified bitrate (5000k in the following case).
>
> Using FFmpeg to create a video stream of around 100 frames from a static
> image.
> The image can be downloaded here:
> http://mightylegends.org/downloads/test01.ppm
>
> The video stream can be downloaded here:
> http://mightylegends.org/downloads/test.m2v
>
>
> Command-line used:
> ~ # cp test01.ppm test02.ppm
>
> ~ # ffmpeg -y -r 1/5 -f image2 -i test%02d.ppm -b 5000k -bufsize 224k
> -maxrate
> 7000k -r pal -f mpeg2video test.m2v
>
> FFmpeg version SVN-rUNKNOWN, Copyright (c) 2000-2006 Fabrice Bellard, et
> al.
>
> configuration:  --prefix=/usr --enable-shared --mandir=/usr/share/man
> --disable-altivec --disable-debug --disable-dv1394 --enable-a52
> --enable-faac --enable-faad --enable-amr_nb --enable-amr_wb
> --enable-amr_if2 --enable-dts --enable-mp3lame --enable-libogg
> --enable-vorbis --enable-x264 --enable-xvid --enable-gpl --enable-pp
> --disable-opts
>   libavutil version: 49.1.0
>   libavcodec version: 51.28.0
>   libavformat version: 51.7.0
>   built on Dec 25 2006 14:05:43, gcc: 4.1.1 (Gentoo 4.1.1-r1)
> Input #0, image2, from 'test%02d.ppm':
>   Duration: 00:00:10.0, start: 0.000000, bitrate: N/A
>   Stream #0.0: Video: ppm, rgb24, 720x576,  0.20 fps(r)
> Output #0, mpeg2video, to 'test.m2v':
>   Stream #0.0: Video: mpeg2video, yuv420p, 720x576, q=2-31, 5000 kb/s,
> 25.00
> fps(c)
> Stream mapping:
>   Stream #0.0 -> #0.0
> Press [q] to stop encoding
> frame=  125 q=7.0 Lsize=     575kB time=5.0 bitrate= 949.0kbits/s
> video:19kB audio:0kB global headers:0kB muxing overhead 2956.040303%

In current SVN, -bufsize is measured in bits, try -bufsize 224kBi

Regards,
V?ctor