[FFmpeg-devel] [PATCH]Implement max_lowres

[Ivan Kalvachev]

On 7/6/10, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Tue, Jul 06, 2010 at 12:01:26AM +0200, Carl Eugen Hoyos wrote:
>> Hi!
>>
>> On Monday 05 July 2010 04:40:59 pm Michael Niedermayer wrote:
>>
>> > > First version attached. Is there an API-change or Changelog entry
>> > > needed?
>> > > Note that this should not be held back because of the obvious
>> > > regressions: ffmpeg -lowres is currently broken for default configure
>> > > anyway;-)
>>
>> > i dont think mpeg1/2 are the only that support lowres
>>
>> As I said, this should currently be no reason to delay this patch.
>
> i disagre
> only codecs that are confirmed to fail / not support it should be limited
> not limit by default and loose feature in all untested codecs

I don't like the whole lowres thing.
Long time ago a friend wanted to use cheap Pentium166 laptop to play
some mpeg4 videos.

In my tests lowres=3 (that is resolution decreases by 8x8, or 1 pixel
per mpeg1/2/4 block) gives just 30% speedup (that is, 70% of the
normal full resolution playback). The same amount of speedup is much
easier achieved by gray only decoding (skip color planes), that also
gives image of much higher quality - full resolution and no
accumulation of decoding artifacts.

Indeed lowres was clever idea and intriguing experiment, but I
consider that it is practically useless.

So I would like to ask, would you consider removing lowres altogether?
It would simplify code and make normal decoding a tiny-bit faster.