Re: [Mjpeg-developer] mpeg2enc with MJPEG Tools 1.9.0rc2 buggy !

[stefan <st...@sf...>]

> First, if you are encoding for DVD do *NOT* use '-q 1 -b 9000'!

Which is very mpeg2enc related. I now know several encoders (ffmpeg 
included), which produce a *lot* less bitrate-spikes and seem to avoid 
them completely in 2-pass-mode ... I have even seen some files where 
there have not been any spikes...

> If you use "-q 3" or "-q 4" the problem appears to go away.
Sorry,... not here... :-(
> Ideally and eventually '-q' should go away completely.  ALl that should
> be specified is a desired average bitrate and a tolerance (how much
> above/below the average is acceptable).
>   
Huh? I don't regard this to be a good idea. There is no harm, if an 
encoder uses less bits than specified by the bitrate. Imagine a 
completly black frame: P+B frames could be close to zero-size (just the 
overhead to say the decoder "same than before"...).

I think, mpeg2enc needs two bitrate-modes:

1) variable bitrate-mode: A local and short second pass is just used to 
chop off bitrate-spikes. That is, whenever the encoder realizes that 
there was a spike, it goes back some frames (a GOP?) and reencodes them 
with a lower q-scale again. But only for that spike...

2) average-bitrate-mode or "filesize-mode": Here it makes some sense to 
specify an upper-bound-tolerance, only. The encoder must not go beyond 
this. If not possible otherwise, then use 2 passes... This mode should 
fit a file as close as possible to a given file-size/average-bitrate...

hmm,... seems like I must use ffmpeg, currently...

cu
Stefan