[MEncoder-users] Terrible results with x264

[belcampo]

James Hastings-Trew wrote:
> On 10-12-23 11:55 AM, belcampo wrote:
>> I would like to learn how dumb I am. My observations:
>> qp gives the most 'constant' quality, less quality variations than crf
>> qp encodes 'significantly' faster than crf.
> You have things a little mixed up. QP does not mean constant quality - 
> it means constant quantizer - its only there for testing purposes and 
> will produce non-optimal output. CRF is what some other encoders (like 
> Handbrake) call "Constant Quality" - it adjusts the quantizers on a 
> frame by frame basis to produce a consistant quality across the video - 
> always what you want.
By using -crf I see this figures come by, it doesn't make the impression 
to me that the quality is 'constant'.
frame=38285 fps= 35 q=31.0 size=  186156kB time=1531.90 bitrate= 
995.5kbits/s   frame=38297 fps= 35 q=30.0 size=  186316kB time=1532.48 
bitrate= 996.0kbits/s   frame=38313 fps= 35 q=29.0 size=  186380kB 
time=1532.86 bitrate= 996.1kbits/s   frame=38327 fps= 35 q=28.0 size= 
186476kB time=1533.44 bitrate= 996.2kbits/s   frame=38342 fps= 35 q=29.0 
size=  186572kB time=1534.02 bitrate= 996.3kbits/s   frame=38359 fps= 35 
q=29.0 size=  186684kB time=1534.78 bitrate= 996.4kbits/s   frame=38376 
fps= 35 q=27.0 size=  186748kB time=1535.36 bitrate= 996.4kbits/s 
frame=38391 fps= 35 q=28.0 size=  186812kB time=1535.94 bitrate= 
996.4kbits/s   frame=38410 fps= 35 q=28.0 size=  186908kB time=1536.70 
bitrate= 996.4kbits/s   frame=38428 fps= 35 q=28.0 size=  187004kB 
time=1537.47 bitrate= 996.4kbits/s   frame=38446 fps= 35 q=26.0 size= 
187068kB time=1538.05 bitrate= 996.4kbits/s   frame=38466 fps= 35 q=26.0 
size=  187196kB time=1538.82 bitrate= 996.6kbits/s   frame=38497 fps= 35 
q=14.0 size=  187307kB time=1539.78 bitrate= 996.5kbits/s   frame=38537 
fps= 35 q=16.0 size=  187403kB time=1541.31 bitrate= 996.0kbits/s 
frame=38558 fps= 35 q=31.0 size=  187531kB time=1542.85 bitrate= 
995.7kbits/s   frame=38574 fps= 35 q=27.0 size=  187691kB time=1543.42 
bitrate= 996.2kbits/s   frame=38610 fps= 35 q=13.0 size=  187825kB 
time=1544.34 bitrate= 996.3kbits/s   frame=38648 fps= 35 q=15.0 size= 
187921kB time=1546.11 bitrate= 995.7kbits/s   frame=38663 fps= 35 q=31.0 
size=  188145kB time=1547.07 bitrate= 996.3kbits/s

I didn't specify a bitrate, but it almost looks like cbr.
q varies from 31 to 13, which is  a very high variation in my opimion. 
Am I misinterpreting matters ??
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