[Ffmpeg-cvslog] r8182 - trunk/doc/TODO

[Baptiste Coudurier]

Hi

Michael Niedermayer wrote:
> Hi
> 
> On Fri, Mar 02, 2007 at 10:54:19AM +0100, Baptiste Coudurier wrote:
>> Hi
>>
>> Nico Sabbi wrote:
>>> bcoudurier wrote:
>>>
>>>> - mpeg2 non linear quantizer
>>>>  
>>>>
>>> is this implemented? how to use it? what are the benefits?
>>>
>> Nope, It's on my TODO, after digging a bit, it seems it would be needed
>> to use a completely different quantization code, since other codecs
>> using mpegvideo.c are using linear one, maybe Im wrong though, some mpeg
>> code is still black magic for me.
>>
>> static const uint8_t non_linear_qscale[32] = {
>>     0, 1, 2, 3, 4, 5, 6, 7,
>>     8,10,12,14,16,18,20,22,
>>     24,28,32,36,40,44,48,52,
>>     56,64,72,80,88,96,104,112,
>> };
>>
>> Benefits is capability to use 1,3,5,7... quantization coefficients, and
>> then going up to 112, which in practice improve very high bitrates
>> quality and also should compress more at (very)low bitrates.
> 
> video above mpeg2 qscale 62 looks too bad to be useable, and below 
> mpeg2 qscale 2 you will not see a difference, the only usefull thing
> in this is maybe 3 and 5

yes this is not useable, sometimes useful for dirty screening at very
low bitrate for equipment only supporting mpeg2...

1,3,5,7 quants offers actually better quality at high bitrates,
you gain granularity. I compared it much using mainconcept encoder,
but yes this is debatable.

> so IMO the whole thing is a waste of time

Well, non linear q is mandatory for D10, since D10 is useful for me, non
linear q is.

-- 
Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA
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