[MEncoder-users] linear quant mapping

[Loren Merritt]

On Sun, 10 Jun 2007, James Tripp wrote:
> Loren Merritt <lorenm at u.washington.edu> wrote:
>
>> What format are you trying to encode? Because the only format I know 
>> of that has such a choice is mpeg2, and libavcodec's mpeg2 encoder
>> doesn't support non-linear quant.
>
> Yes mpeg2.
> I'm suprised, why not?
> I thought non-linear mpeg2 standard. Linear only for mpeg1 and 
> available for mpeg2. I assumed non-linear, as all mpeg2 encoders I've 
> used default to non-linear and not many even have a linear option.

I wasn't the one who implemented it so I can't say for sure, but the 
obvious reason is:
libavcodec has one codepath that handles mpeg1, mpeg2, mpeg4, h261, h263, 
and variants thereof, with only minor differences in the bitstream writing 
part. mpeg2 linear quant is the same as all those other formats (or at 
least, it just requires some parameters to the quantization function), 
while mpeg2 non-linear quant would require extra code.

--Loren Merritt