[Libav-user] Why low qmax value improve video quality?
night.rain.whisper at gmail.com
Mon Sep 2 20:39:23 CEST 2013
Quantization parameter is the denominator of element-wise division.
So increasing QP will increase a number of lost bits of information
about a picture and therefore lower image quality.
2013/9/2 theateist84 <theateist at gmail.com>:
> Maybe my questions doesn't make sense due to not understanding but please
> explain me what I miss because I did read posts and wiki and still it's not
> clear to me.
> As I understand setting low value for qmax will improve the quality by
> increasing the bitrate. Maybe I didn't understood something but isn't lowing
> the Q(quantization) will decrease the quantization levels and thus the
> bitrate which means degradation in quality? Or in ffmpeg lowing Q means
> increasing the quantization levels? If the last is true so it make sense
> that lower qmax improves the quality.
> If the above is true, so increasing qmax will decrease the quantization
> levels which means less bits for coding a quantization level. So, if number
> of bits for a level is lower, so total bits per frame will be lower, so how
> the encoder manage to get to the desired bitrate?
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