CRF value not working when encoding with libaom in AV1 (2)

[Ewout]

Excuse me for reporting inconclusive data in my first ticket (#7483).

Summary of the bug: CRF value not working when encoding with libaom in AV1
How to reproduce:

ffmpeg -i C:\Morocco8khdr60fps-1280.m4v -c:v libaom-av1 -crf 6 -strict experimental av1_test_Morocco8K_1280crf6.mkv
ffmpeg -i C:\Morocco8khdr60fps-1280.m4v -c:v libaom-av1 -crf 12 -strict experimental av1_test_Morocco8K_1280crf12.mkv
ffmpeg -i C:\Morocco8khdr60fps-1280.m4v -c:v libaom-av1 -crf 18 -strict experimental av1_test_Morocco8K_1280crf18.mkv
ffmpeg -i C:\Morocco8khdr60fps-1280.m4v -c:v libaom-av1 -crf 24 -strict experimental av1_test_Morocco8K_1280crf24.mkv

ffmpeg version: ffmpeg-20181007-0a41a8b-win64-static
built on: Windows 10 64-bit (1809)

I encoded a high-bitrate m4v file (encoded with x264) to AV1 with different CRF values. All came out with the same bitrates. See the attached screenshots. Files can be found here: ​https://drive.google.com/file/d/1e4QmCXavsJqxzI4OOS5jqfMmSSmGPD4B/view?usp=sharing

The input file was 16 MB, around 1 MB/s. With CRF values of 6, 12, 18 and 24 they all encoded to the same 836 kB (855.592 bytes), around 52 kB/s.

[Ewout]

Encode settings

[Ewout]

Encode results

[Carl Eugen Hoyos]

Why do you believe this is an issue that can be fixed in FFmpeg?

[Ewout]

jamrial ​updated the ​AV1 encode wiki by adding that -b:v needs to be specified, where -b:v 0 gives a constant quality and -b:v int gives a constant quality with max bit-rate int.

I will test today if this fixes the issue.