[FFmpeg-devel] MPEG-2 encoder question

[Jonathan Campbell]

I see. So my encoder program using the API needs to set macroblock 
decision mode to "best rate distortion" and set the QP_RD flag. And 
apparently, disable scene change detection. No modification to the 
source needed. Thanks!

I also wanted to ask if MPEG-2 field picture encoding is implemented in 
FFMPEG. I don't mean interlaced frame encoding with +ilme and +ildct I 
mean field pictures, MPEG-2 picture types 1 (top field) and 2 (bottom 
field) instead of picture type 3 (frame encoding).

> On Tue, Jan 03, 2012 at 12:09:44PM -0800, Jonathan Campbell wrote:
>> I'm looking at libavcodec/mpegvideo_enc.c and encode_thread(). It
>> uses s->qscale for the entire set of macroblock rows assigned to it
>> (start_mb_y to end_mb_y), which means that it uses the same fixed
>> quantization for the /entire frame/.
>>
>> Couldn't we improve the encoder by dynamically changing the qscale
>> per macroblock row, or even mid-row? I know for a fact the MPEG-1/2
>> video standard has macroblock codes to allow for it, so why is
>> FFMPEG not taking advantage of it?
>>
>> Anyone else here worked on this? I'm willing to patch
>> mpegvideo_enc.c to do this and submit upstream to make FFMPEG a
>> better MPEG-2 encoder.
> please see the qp_rd code that adjust qp per MB, and the various
> psychovissual variables from the ratecontrol code.
>
> Iam sure things can be improved and such improvments are very welcome
> but qscale is not a constant within a row
>
> [....]
>
>
>
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