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

[temp2010 at forren.org]

Renato,

How would one go about rendering the stream for only the luminance plane?
 Do you mean going into my MF H.264 encoder?  You must.  Otherwise I don't
know how to analyze the compressed output to omit the color.  And for the
MF H.264 encoder, I don't think there's any way to tell it to do only Y.
 Is this what you were suggesting?  If so, then how would one get around
the problem I just indicated?  If not, what did you really mean.


On Fri, Jan 4, 2013 at 8:47 AM, Renato MAURO (Libero) <renatomauro at libero.it
> wrote:

>  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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