[x264-devel] [x264] quality of first I frame is very poor

[Sandip Ray]

Dear Experts,

I downloaded x264 source code from git://git.videolan.org/x264.git and built x264.exe in Visual Studio. I set command line parameters as follows.

-v --frames 300 -B 128 -o D:/output/foreman.264 D:/output/foreman_cif.yuv 352x288

I observe that QP in the first I frame is very high, resulting in poor quality. The output from the code is as follows.  

x264 [debug]: level_idc: 13
x264 [info]: using cpu capabilities: MMX2 SSE2 SSE3 Cache64 Slow_mod4_stack
x264 [debug]: frame=   0 QP=50.99 NAL=3 Slice:I Poc:0   I:396  P:0    SKIP:0
size=642 bytes PSNR Y:24.65 U:36.67 V:37.33 SSIM Y:0.71029

I guess default parameter settings are optimal. Hence I am surprised why quality is so poor in first I frame.

Can anyone let me know what goes wrong here ? 

Thanks and Regards,
Sandip
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