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, [email protected] 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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