8:9 video outputs stretched 16:9

ghost commented 4 years ago

mpv version and platform

Windows 10 Enterprise v.1809

mpv 0.29.0-353-g65b1c2d065 Copyright © 2000-2019 mpv/MPlayer/mplayer2 projects
 built on Sun Jul 14 20:16:49 +08 2019
ffmpeg library versions:
   libavutil       56.30.100
   libavcodec      58.53.101
   libavformat     58.28.102
   libswscale      5.4.101
   libavfilter     7.56.101
   libswresample   3.4.100
ffmpeg version: git-2019-07-13-f86f213a

Description

Creating a webm using source material that is 8:9 make the webm output stretched widescreen video screenshot showing source on top, output webm on bottom

Log file

log file

ghost commented 4 years ago

I just updated the webm converter script and MPV just to be sure, and the problem persists.

ekisu commented 4 years ago

I can't reproduce it, at least not with this video (used youtube-dl to download it).

Could you run the encoding command:

.\mpv.com "I:\! TV\Trailer Park Boys\Season 06\Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv" --output=log-encode.txt --start=0:01:09.903 --end=0:01:20.714 --ovc=libvpx --oac=libvorbis --loop-file=no --vid=1 --aid=no --sid=no --sub-ass-override=yes --sub-auto=exact --sub-delay=0.000000 --video-rotate=0 --ovcopts-add=threads=12 "--oset-metadata=title=%60%Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3" --ovcopts-add=b=2212k --ovcopts-add=crf=10 --ovcopts-add=flags=+pass2 "-o=I:\Pictures\WebM/Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv-[01.09.903-01.20.714].webm"

in a cmd/PowerShell window and send me the "log-encode.txt", and the cmd window output?

ghost commented 4 years ago

I can't reproduce it, at least not with this video (used youtube-dl to download it).

Could you run the encoding command:

.\mpv.com "I:\! TV\Trailer Park Boys\Season 06\Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv" --output=log-encode.txt --start=0:01:09.903 --end=0:01:20.714 --ovc=libvpx --oac=libvorbis --loop-file=no --vid=1 --aid=no --sid=no --sub-ass-override=yes --sub-auto=exact --sub-delay=0.000000 --video-rotate=0 --ovcopts-add=threads=12 "--oset-metadata=title=%60%Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3" --ovcopts-add=b=2212k --ovcopts-add=crf=10 --ovcopts-add=flags=+pass2 "-o=I:\Pictures\WebM/Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv-[01.09.903-01.20.714].webm"

in a cmd/PowerShell window and send me the "log-encode.txt", and the cmd window output?

C:\Program Files\MPV>.\mpv.com "I:\! TV\Trailer Park Boys\Season 06\Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv" --output=log-encode.txt --start=0:01:09.903 --end=0:01:20.714 --ovc=libvpx --oac=libvorbis --loop-file=no --vid=1 --aid=no --sid=no --sub-ass-override=yes --sub-auto=exact --sub-delay=0.000000 --video-rotate=0 --ovcopts-add=threads=12 "--oset-metadata=title=%60%Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3" --ovcopts-add=b=2212k --ovcopts-add=crf=10 --ovcopts-add=flags=+pass2 "-o=I:\Pictures\WebM\1.webm"
Error parsing option output (option not found)
Setting commandline option --output=log-encode.txt failed.

Exiting... (Fatal error)

changing --output to log-file gives:

C:\Program Files\MPV>.\mpv.com "I:\! TV\Trailer Park Boys\Season 06\Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv" --log-file=log-encode.txt --start=0:01:09.903 --end=0:01:20.714 --ovc=libvpx --oac=libvorbis --loop-file=no --vid=1 --aid=no --sid=no --sub-ass-override=yes --sub-auto=exact --sub-delay=0.000000 --video-rotate=0 --ovcopts-add=threads=12 "--oset-metadata=title=%60%Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3" --ovcopts-add=b=2212k --ovcopts-add=crf=10 --ovcopts-add=flags=+pass2 "-o=I:\Pictures\WebM\1.webm"
Playing: I:\! TV\Trailer Park Boys\Season 06\Trailer Park Boys - S06E05 - Halloween 1977 - DVD - x264 AC3.mkv
 (+) Video --vid=1 (*) (h264 720x476 29.970fps)
     Audio --aid=1 --alang=eng (*) (ac3 6ch 48000Hz)
VO: [lavc] 720x476 => 720x535 yuv420p
[vo/lavc] Reading 2-pass log: I:\Pictures\WebM\1.webm-video-pass1.log
[file] Cannot open file 'I:\Pictures\WebM\1.webm-video-pass1.log': No such file or directory
Failed to open I:\Pictures\WebM\1.webm-video-pass1.log.
[vo/lavc] could not open 'I:\Pictures\WebM\1.webm-video-pass1.log', disabling 2-pass encoding at pass 2
[vo/lavc] Opening encoder: libvpx VP8 [libvpx]
[encode] Opening output file: I:\Pictures\WebM\1.webm
[encode] Opening muxer: WebM [webm]
V: 00:01:20 / 00:22:39 (5%) {0.0min 53.7fps 2.1MB}

[encode] video: encoded 2764143 bytes
[encode] audio: encoded 0 bytes
[encode] muxing overhead 2994 bytes

Exiting... (End of file)

log-encode.txt

ghost commented 4 years ago

another log, using the script like I normally do from withing MPV (shift-w) and this time having "run detached=false"

using --log-file in mpv.conf log.txt at webm (output) directory log.txt at source (mkv) directory

ghost commented 4 years ago

Apparently it doesn't happen when I use the same script to convert to MP4, the problem seems to only happen when using WEBM as output.

Top = source, bottom is output MP4.

screenshot

ekisu commented 4 years ago

Well, your video isn't 4:3, but actually 8:9. I don't know if VP8 specifically forces an aspect ratio, but as you said that using MP4 as the output format, I'd assume so.

ghost commented 4 years ago

Well, your video isn't 4:3, but actually 8:9. I don't know if VP8 specifically forces an aspect ratio, but as you said that using MP4 as the output format, I'd assume so.

yeah sorry, it's not 4:3, but is there a way to prevent VP8 from ruining the aspect ratio?

ekisu commented 4 years ago

I hope so. Could you upload the clip you made, in MP4? I want to see if ffmpeg also forces the aspect ratio when using VP8.

ghost commented 4 years ago

I hope so. Could you upload the clip you made, in MP4? I want to see if ffmpeg also forces the aspect ratio when using VP8.

MP4 output

ghost commented 4 years ago

Someone pointed out this might be the issue: libvpx vpxenc.c#L1037

ekisu commented 4 years ago

ffmpeg doesn't have this issue, apparently. Using:

ffmpeg.exe -i 89input.mp4 -c:v libvpx -c:a libvorbis 89output.webm

Results in a video with correct proportions.

ghost commented 4 years ago

ffmpeg doesn't have this issue, apparently. Using:
ffmpeg.exe -i 89input.mp4 -c:v libvpx -c:a libvorbis 89output.webm
Results in a video with correct proportions.

then how do I get this webm script for mpv to do the same?

ekisu commented 4 years ago

I don't know. Looking deeper on it, this seems more like a bug on ffmpeg/mpv itself. mpv passes the SAR (along with other codec parameters) in the codecpar field on the AVStream struct. Starting from the mpv code:

SAR is detected, and set into the AVCodecContext struct here;
Here, these parameters are copied into a AVCodecParameters struct; these parameters are then copied into the AVStream struct here.

Now, we begin looking at the ffmpeg side of the things:

Both Matroska (WebM container) and MOV (MP4 container) write the SAR data (Matroska actually writes the display aspect ratio, but for all intents it works the same) into the file header. However, a crucial difference is from where this data is read. The Matroska muxer reads it from the sample_aspect_ratio field in the AVStream struct (which wasn't set by mpv), while the MOV container reads it from from the sample_aspect_ratio in the codecpar field, which was set by mpv. I'm pretty sure this is why MP4 output works, and why WebM output doesn't.
So, which field should mpv set? Apparently, both. Looking at the init_muxer function, which is called by avformat_write_header (via avformat_init_output), it actually checks whether both fields differ, and warns about it... Well, unless only one of them is set. If this happens, the "unset" value (at least when the AVStream sample_aspect_ratio one is unset) will default to a numerator of 0 and a denominator of 1, and the warning won't go off.

I will probably build mpv myself to test my theory, when I have some time...

edit: I've submitted this PR to mpv, which should fix this.

ekisu commented 4 years ago

Fixed in upstream.

ekisu / mpv-webm