[XviD-devel] Ask xvid 1.1.2 single pass about target bitrate

[Robert Swain]

Fu-Hsien Lin wrote:
 > -i H:\sequence\foreman_cif.yuv -w 352 -h 288 -type 0 -o 
I:\test112\xvid_1_1_2_.m4v -framerate 30.0
 > -bitrate 512000 -quality 6 -single -stats   -max_key_interval  15
 > I try to use single pass for target bitrate
 > use formen_cif sequence
 > file size 772,380bytes
 > avg  size 2574bytes
 >
 > 2574bytes* 8(bits) * 30(frame rate)=617.76kbites/sec
 >
 > Is it right?
 > but, i set target bitrate =  512kbits/sec
 > the result bitrate is 617.76 kbits/sec
 > this result bitrate seem to big
 >
 > i check the QP
 > the rate control is work.
 >
 > I do not know what's wrong?
 > do i miss something??
 > anything about this...

I don't think you've missed anything. The foreman video is quite short and the 
XviD rate control mechanism doesn't appear to be very good at hitting target bit 
rates on short clips. You may experience better results using the 2 pass mode.

Regards,
Rob