[FFmpeg-trac] #8344(ffprobe:new): ffprobe does not recognize yava420p format (alpha channel) for webm
FFmpeg
trac at avcodec.org
Wed Oct 30 15:59:34 EET 2019
#8344: ffprobe does not recognize yava420p format (alpha channel) for webm
-------------------------------------+-------------------------------------
Reporter: jhaand | Type: defect
Status: new | Priority: normal
Component: ffprobe | Version:
Keywords: alpha | unspecified
channel | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
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
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8344>
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