search

kim42083 / webm

Automatically exported from code.google.com/p/webm
0 stars 0 forks source link

keyframe popping on single-pass constant quality mode is very noticeable #382

Open GoogleCodeExporter opened 9 years ago

GoogleCodeExporter commented 9 years ago 
What is the expected behavior? What do you see instead?

When using a fixed quantizer setting, such as minq=15 and maxq=15, one would 
expect visual quality to stay relatively constant (as many other encoders 
implement constant quantizer to be similar to a virtual constant quality).

However, doing so in single-pass yields relatively inconsistent visual quality 
in the form of visual quality "popping", where details of a fairly static scene 
will appear and disappear at the keyframe interval.

What version are you using? On what operating system?
Up to the latest release, on Linux (Fedora 16).

Can you reproduce using the vpxdec or vpxenc tools? What command line are
you using?

Yes, this happens with vpxenc as well as ffmpeg using the libvpx encoder.  
Example parameters would be:

cat the-input.y4m | vpxenc --output=here-lies-the-output.webm --best --verbose 
--q-hist=16 --rate-hist=16 --threads=4 --end-usage=vbr --min-q=25 --max-q=25 
--kf-max-dist=250 --tune=ssim -

Please provide any additional information below.

Original issue reported on code.google.com by basilgo...@gmail.com on 16 Dec 2011 at 9:29

GoogleCodeExporter commented 9 years ago

Original comment by iss...@webmproject.org on 16 Dec 2011 at 9:30

GoogleCodeExporter commented 9 years ago

Original comment by albe...@google.com on 16 Feb 2012 at 9:09

GoogleCodeExporter commented 9 years ago

Original comment by albe...@google.com on 8 Mar 2012 at 12:08

GoogleCodeExporter commented 9 years ago 
If the implementation of this mode is with a fixed quantizer, then this popping 
inherent to the algorithm. The keyframe quantizers are on a slightly different 
scale than the interframe quantizers. In terms of a "constant quality mode," 
this is an implementation detail. I think this issue can be rephrased as an 
enhancement request to provide a constant quality mode.

Original comment by jkoles...@google.com on 24 May 2012 at 6:34