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Old 18th August 2016, 09:19   #77  |  Link
Jamaika
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Join Date: Jul 2015
Posts: 697
Codec AV1-git-d847070 is still underdeveloped. Problems or inconsistencies resulting from the explanation of some functions.

The problem of different bitrates.
aomenc.exe -v --threads=4 --width=1920 --height=1080 --i420 --profile=0 --fps=30000/1001 --best --codec=av1 --cpu-used=0 --passes=2 --pass=2 --fpf=aom.pass --drop-frame=100 --kf-max-dist=60 --target-bitrate=3500 --frame-boost=1 --end-usage=cbr --gf-cbr-boost=300 --max-intra-rate=110 --bias-pct=50 --maxsection-pct=3000 --aq-mode=1 --kf-max-dist=60 --color-space=bt709
or
aomenc.exe -v --threads=4 --width=1920 --height=1080 --i420 --profile=0 --fps=30000/1001 --best --codec=av1 --cpu-used=0 --passes=2 --pass=2 --fpf=aom.pass --drop-frame=100 --kf-max-dist=60 --target-bitrate=0 --cq-level=34 --frame-boost=1 --end-usage=q --bias-pct=50 --gf-cbr-boost=200 --max-inter-rate=130 --maxsection-pct=2000 --aq-mode=1 --kf-max-dist=60 --color-space=bt709

The loss of video quality at the bitrate of 3500kbps, in fact 4000-4300kbps depending on the mode aq-mode.
For mode VBR (default) is a significant drop in compression frame {about 400KB for PNG} in relation to the original. It is synonymous with a decrease in quality. The biggest issue is slightly rough surfaces that lose their roughness and are sharp edges ex. subtitles. For the X265 {veryslow} is the order of 300kb, which is less lost data and has set value bitrate for 2pass.

Overview the functions:
"drop-frame" is correct display frame rates for movies about XX000/1001 fps. Not the task of this function is that the value fps is overvalued and is a little greater, eg. 30.033. In fact, the codec itself should adapt dropframe without the user's knowledge, but it is not. For mode CBR function "drop-frame" is with errors.
"gf-cbr-boost" mode golden frame (P or B). The construction of this frame is mysterious and complex. These frames aren't displayed and retain data for the P-frame depend on the function "auto-alt-ref". The best setting codec when turned off "auto-alt-ref". To try to match the quality of CBR to VBR is to raise bitrate golden frame by 300%. The value of the frame I by 110%. Note: Do not turn on the "frame-boost". This function is only for mode "end-usage=q".
"bias-pct" is a hash of two modes frames VBR and CBR. How not to set the best variant is 50% to 50%. Otherwise, the film is visibly pale.
"color-space" bt2020. It is now fiction. As you know ffmpeg converter converts the bt601 and then to the set. In addition, the codec is 8 bit.
"maxsection-pct" as not to describe it is a dead function. Change the value with 2000% to 3000% doesn't contribute to improving the quality of frames???

Last edited by Jamaika; 18th August 2016 at 15:15.
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