[FFmpeg-trac] #10220(undetermined:new): AVIF image's alpha track is not being found

[FFmpeg]

#10220: AVIF image's alpha track is not being found
-------------------------------------+-------------------------------------
             Reporter:  Meten        |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:  av1 libaom-  |               Blocked By:
  av1                                |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 ffmpeg/ffprobe don't show or can't "see" that there is a 2nd alpha track
 for an AVIF image that does have one.

 How to reproduce:
 Create an AVIF image with an alpha layer
 (Using avifenc to create a new AVIF file in a similar fashion will yield
 similar results)
 {{{
 % ffmpeg -hide_banner -i icon.png -c:v libaom-av1 -cpu-used 0 -still-
 picture true -crf:0 56 -crf:1 40 -filter_complex
 'split[rgb],alphaextract[a]' -pix_fmt:0 yuv420p -map '[rgb]' -map '[a]'
 newicon.avif
 }}}
 Try to do anything with it like e.g. convert it back to a PNG, and FFmpeg
 will complain:
 {{{
 % ffmpeg -hide_banner -i newicon.avif -filter_complex
 "[0:v:1][0:v:0]alphamerge[out]" -map '[out]' out.png
 [libdav1d @ 000002a98be16e00] libdav1d 1.1.0-0-g9593e62
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'newicon.avif':
   Metadata:
     major_brand     : avif
     minor_version   : 0
     compatible_brands: avifmif1miafMA1B
   Duration: N/A, start: 0.000000, bitrate: N/A
   Stream #0:0[0x1]: Video: av1 (Main), yuv420p(tv,
 unknown/bt709/iec61966-2-1), 184x184 [SAR 1:1 DAR 1:1], 1 fps, 1 tbr, 1
 tbn
 Stream specifier ':v:1' in filtergraph description
 [0:v:1][0:v:0]alphamerge[out] matches no streams.
 }}}
 version used:
 {{{
 ffmpeg version 2023-02-22-git-d5cc7acff1-full_build-www.gyan.dev Copyright
 (c) 2000-2023 the FFmpeg developers
   built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
 }}}

 Interestingly, ffprobe does show the alpha track for animated AVIF files.
 Example:
 {{{
 % ffprobe -hide_banner animated_logo.avif
 [libdav1d @ 0000018448b99140] libdav1d 1.1.0-0-g9593e62
 [libdav1d @ 0000018448b9a780] libdav1d 1.1.0-0-g9593e62
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\animated_logo.avif':
   Metadata:
     major_brand     : avis
     minor_version   : 0
     compatible_brands: avisavifmsf1iso8mif1miafMA1B
   Duration: 00:00:01.40, start: 0.000000, bitrate: 69 kb/s
   Stream #0:0[0x1](und): Video: av1 (Main) (av01 / 0x31307661),
 yuv420p(tv, progressive), 256x256 [SAR 1:1 DAR 1:1], 14 kb/s, 15 fps, 15
 tbr, 100k tbn (default)
     Metadata:
       handler_name    : PictureHandler
       vendor_id       : [0][0][0][0]
       encoder         : Lavc60.4.100 libaom-av1
   Stream #0:1[0x2](und): Video: av1 (Main) (av01 / 0x31307661), gray(pc,
 gbr/unknown/unknown, progressive), 256x256 [SAR 1:1 DAR 1:1], 42 kb/s, 15
 fps, 15 tbr, 100k tbn
     Metadata:
       handler_name    : PictureHandler
       vendor_id       : [0][0][0][0]
       encoder         : Lavc60.4.100 libaom-av1
 [libdav1d @ 0000018448b9b400] libdav1d 1.1.0-0-g9593e62
 [libdav1d @ 0000018448b8aac0] libdav1d 1.1.0-0-g9593e62
 }}}
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10220>
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