[Live-devel] How to release frame; How to improve horrible video quality

[Renato MAURO (Libero)]

NV12 is similar to I420 (or YUV420, if you prefer), so it is 12 bit per 
pixel, 8 for luminance and 4 for CrCb (or U and V if you prefer). See 
http://www.fourcc.org/yuv.php#NV12.
Obviously, "4 bits for CrCb" means that each byte is used for 4 pixels 
(a 2x2 quad), and so NV12 is a planar only format.

So: 640 x 480 x 1,5 = 450 kBi = 3.51 Mbi uncompressed => 3.51 Mbi / 160 
kbi = 22,5 times.

I suggest to render the stream for the luminance plane only (like old TV 
sets!!): if you get a good output, the problem is the way the renderer 
works on the U and V plane.


Regards,

     Renato


Il 04/01/2013 13.49, temp2010 at forren.org ha scritto:
> Thanks very much for your help, Ross.
>
> BACKGROUND: (CLARIFICATION ONLY) Indeed I only have one thread calling 
> doEventLoop().  That's all I meant by my penultimate background 
> sentence.  The last background sentence points out a separate thread 
> for MF, that's independent of Live555, and is in fact the thread 
> taking advantage of the one exception within Live555: calling 
> triggerEvent().
>
> FOLLOWUP QUESTION: Having incorporated your question one answer, my 
> output is better and now only "very poor" rather than "horrible".  My 
> uncompressed stream is 640 x 480 x 30fps.  It passes through NV12 
> format, which when considered as YUV I think has about 16 bits of info 
> per pixel (8 bits for Y, 8 bits for UV, like YUV422).  So an 
> uncompressed 640 x 480 frame should have nearly 5Mbits of info. 
>  However, the compressed frames I'm sending to Live555 are generally 
> 160kbits each (after an initial 384kbit frame).   I realize you're not 
> responsible for MF, but perhaps you can give your opinion, 
> please. This suggests to me that my MF H.264 encoder is compressing 
> roughly 5Mbits/160kbits = 31 times.  Perhaps my remaining "very poor" 
> quality is because this is too much compression.  I reconfigured the 
> encoder for 10 times the average bit rate, but this typical 
> 160kbits/frame output size didn't really change.  DO YOU AGREE that I 
> ought to be able to increase encoder output quality by increasing 
> average bit rate, and that the 160kbits per compressed frame should 
> rise toward 5Mbits?
>
> Thanks again.
>
>
>
>
>
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