Issue 1857 in webm: Forced key frame causes low quality after key frame

[matti… via monorail]

Status: Untriaged
Owner: ----
Labels: Type-Bug Pri-2
Components: libvpx

New issue 1857 by matti...@gmail.com: Forced key frame causes low quality after key frame
https://bugs.chromium.org/p/webm/issues/detail?id=1857

What is the expected behavior?

Forced key frame would not affect quality significantly.

What do you see instead?

Low quality after forced key frame.

What version are you using? On what operating system?

# macOS with ffmpeg 7.0.1 and libvpx 1.13.1 from brew
$ ffmpeg -hide_banner -version
ffmpeg version 7.0.1 Copyright (c) 2000-2024 the FFmpeg developers
built with Apple clang version 15.0.0 (clang-1500.3.9.4)
configuration: --prefix=/opt/homebrew/Cellar/ffmpeg/7.0.1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags='-Wl,-ld_classic' --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libharfbuzz --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libssh --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox --enable-neon
libavutil 59. 8.100 / 59. 8.100
libavcodec 61. 3.100 / 61. 3.100
libavformat 61. 1.100 / 61. 1.100
libavdevice 61. 1.100 / 61. 1.100
libavfilter 10. 1.100 / 10. 1.100
libswscale 8. 1.100 / 8. 1.100
libswresample 5. 1.100 / 5. 1.100
libpostproc 58. 1.100 / 58. 1.100


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

Can be reproduce with ffmpeg with attached script. I don't know if the bug is in ffmpeg or libvpx yet.

Script generates a test source that can reproduce the issue then encodes it using h264 and libvpx-vp9 to show that same settings and h264 does not produce low quality.

Also see comments at the top of the script for some findings.

Attachments:
vp9-forced-key-frame-artifacts.sh 1.1 KB

--
You received this message because:
1. The project was configured to send all issue notifications to this address

You may adjust your notification preferences at:
https://bugs.chromium.org/hosting/settings

[matti… via monorail]

Comment #1 on issue 1857 by matti...@gmail.com: Forced key frame causes low quality after key frame
https://bugs.chromium.org/p/webm/issues/detail?id=1857#c1

The bad quality happens when switching from the noisy video to the black background with text. For a while the quality of the text is good but then artifacts show up.

[matti… via monorail]

Comment #2 on issue 1857 by matti...@gmail.com: Forced key frame causes low quality after key frame
https://bugs.chromium.org/p/webm/issues/detail?id=1857#c2

Output from script. Notice for output.libvpx-vp9.mp4 the quailty changes at ~12s. With different noisy video duration the time it takes changes a bit.

Attachments:
output.libvpx-vp9.mp4 2.3 MB
output.h264.mp4 2.8 MB