Opened 5 years ago
Last modified 5 years ago
#8344 new enhancement
ffprobe does not recognize yuva420p format (alpha channel) for webm
Reported by: | Jelle Haandrikman | Owned by: | |
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Priority: | wish | Component: | avcodec |
Version: | git-master | Keywords: | alpha vp8 vp9 |
Cc: | Blocked By: | ||
Blocking: | Reproduced by developer: | no | |
Analyzed by developer: | no |
Description
Summary of the bug: ffprobe does not recognize the alpha channel. Even when I encode a webm file from png files with alpha channel using ffmpeg.
How to reproduce:
ffmpeg -i inside_the_box_%04d.png -r 30 inside_the_box.webm ffprobe inside_the_box.webm
The output from ffmpeg shows:
[libvpx-vp9 @ 0x55ecc6b67f80] v1.8.1 Output #0, webm, to 'inside_the_box.webm': Metadata: encoder : Lavf58.20.100 Stream #0:0: Video: vp9 (libvpx-vp9), yuva420p, 1080x1920, q=-1--1, 200 kb/s, 30 fps, 1k tbn, 30 tbc Metadata: encoder : Lavc58.35.100 libvpx-vp9 Side data: cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
When I check the output file, the alpha channel is not recognised. It recognises the stream as yuv420p and not as yuva420p.
Input #0, matroska,webm, from 'inside_the_box.webm': Metadata: ENCODER : Lavf58.20.100 Duration: 00:00:30.07, start: 0.000000, bitrate: 95 kb/s Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 1080x1920, SAR 1:1 DAR 9:16, 30 fps, 30 tbr, 1k tbn, 1k tbc (default) Metadata: alpha_mode : 1 ENCODER : Lavc58.35.100 libvpx-vp9 DURATION : 00:00:30.066000000
This makes creating and displaying a video with alpha transparency hard to accomplish.
Ffplay also has the same issue.
If I check the file using Firefox and Chrome the alpha channel is included in the .webm file.
Also when playing the file using mpv --vd=libvpx-vp9 --alpha=yes inside_the_box.webm
The alpha channel is shown on the display.
Tested on Debian-testing with ffmpeg: 4.1.4-1+b3 amd64
Change History (3)
comment:1 by , 5 years ago
Summary: | ffprobe does not recognize yava420p format (alpha channel) for webm → ffprobe does not recognize yuva420p format (alpha channel) for webm |
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comment:2 by , 5 years ago
comment:3 by , 5 years ago
Component: | ffprobe → avcodec |
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Keywords: | vp8 vp9 added; channel removed |
Priority: | normal → wish |
Type: | defect → enhancement |
Version: | unspecified → git-master |
The native VP8/9 decoders don't decode alpha but libvpx does, and ffprobe uses native decoders for a stream when available. At present, there's no facility to force a specific decoder for streams.