Issue 1739 in webm: libvpx transcoding with temporal layers results in artifacts with a specific file

[arka… via monorail]

Status: Unconfirmed
Owner: ----

New issue 1739 by arka...@gmail.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739

How to reproduce
----------------

1. Use ffmpeg v4.4
2. Use the attached `broken-video.mp4` video file
3. Transcode it with the following command:

```
ffmpeg -nostdin -y -i broken-video.mp4 -vf scale=1920:1080:force_original_aspect_ratio=decrease -c:v libvpx -b:v 2000k -ts-parameters ts_number_layers=3:ts_target_bitrate=500,1000,2000:ts_rate_decimator=4,2,1:ts_periodicity=4:ts_layer_id=0,2,1,2:ts_layering_mode=4 -c:a libopus -b:a 128k -ac 2 -f webm broken-video.webm
```

4. Check out the result (attached `broken-video.webm`)



What happened?
==============

The video will have visible artifacts and an inadequate level of quantization (see attached `broken-video.webmp`)

The issue is fixed if `qpmax` is limited to `31` and below or temporal layers options are removed (or reduced to 1)

That issue is not reproducible if other video files are used so it must be something in attached video file which triggers the issue.

An example of a heavier video that produces totally fine video with the same parameters is https://www.dropbox.com/s/eif3b898klbbx79/ok-video.mp4?dl=0.


What's expected?
================

The video should look fine and have similar video quality

Attachments:
broken-video.mp4 8.7 MB
broken-video.webm 3.0 MB

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[jz… via monorail]

Updates:
Cc: mar...@google.com kys...@google.com ji...@google.com

Comment #1 on issue 1739 by jz...@google.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739#c1

> Use ffmpeg v4.4

Thanks for the report, can you add what version of libvpx that was built against and what platform you're running on? When doing an encode the wrapper will output something like:
[libvpx @ 0x...] v1.10.0-119-g15a75b453

[arka… via monorail]

Comment #3 on issue 1739 by arka...@gmail.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739#c3

Video was attempted to encode on different machines. One is Mac OS 11.5.2 with libvpx v1.10.0, and on remote server it's Alpine with libvpx 1.10.0-33-g1c792f299. The result is same

[jz… via monorail]

Updates:
Cc: -mar...@google.com
Labels: -Needs-Feedback
Owner: mar...@google.com
Status: Assigned

Comment #4 on issue 1739 by jz...@google.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739#c4

(No comment was entered for this change.)

[mar… via monorail]

Comment #5 on issue 1739 by mar...@google.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739#c5

I was able to repro with the ffmpeg command, but have been unable to reproduce directly in libvpx with the same/similar input.

Temporal layers in libvpx are tested with the sample encoder vpx_temporal_svc_encoder.c; temporal layers have only been used for RTC mode (real-time, lag=0, CBR rate control). Running that sample encoder for vp8 with 3 temporal layers i was unable to repro the artifact so far..

Can you try adding "-deadline realtime -rc_lookahead 0 -minrate 2000k -maxrate 2000k -qmax 56" to ffmpeg command to test the mode TL has been used for (setting qmax 56 to avoid poor quality at 63(default))?

Also is this only for vp8, or do also see issues with vp9 (libvpx-vp9)?

[mar… via monorail]

Updates:
Status: WontFix

Comment #7 on issue 1739 by mar...@google.com: libvpx transcoding with temporal layers results in artifacts with a specific file
https://bugs.chromium.org/p/webm/issues/detail?id=1739#c7

Unable to reproduce in libvpx. Re-open if feedback is provided to comment#5.