default ffmpeg test pattern - multiple playback issues

[Bossett]

Describe the bug

See https://bsky.app/profile/bossett.social/post/3l3wru4mlxy2j. The ffmpeg testrc pattern in 1920x1080 @ 120fps causes a number of playback issues.

To Reproduce

Generate a test file using ffmpeg mp4 defaults:

ffmpeg -f lavfi -i testsrc=duration=59:size=1920x1080:rate=120 testsrc.mp4

Upload file, and view on mobile (and some other platforms)

Expected behavior

No errors

Screenshots

(others in thread)

Details

• Platform: iOS (others reported)
• Platform version: 17.6.1
• App version: 1.91

Additional context

https://bsky.app/profile/bossett.social/post/3l3wssuiaju2i - also resizes slightly when hitting play on web, where it works

https://github.com/user-attachments/assets/a42e6f6d-c356-41a9-a117-1c945526e345 is the video original and media info:

General
Format                      : MPEG-4
Format profile              : Base Media
Codec ID                    : isom (isom/iso2/avc1/mp41)
File size                   : 2.88 MiB
Duration                    : 59 s 0 ms
Overall bit rate            : 409 kb/s
Frame rate                  : 120.000 FPS
Writing application         : Lavf58.64.100

Video
ID                          : 1
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : High 4:4:4 Predictive@L5.1
Format settings             : CABAC / 4 Ref Frames
Format settings, CABAC      : Yes
Format settings, Reference  : 4 frames
Codec ID                    : avc1
Codec ID/Info               : Advanced Video Coding
Duration                    : 59 s 0 ms
Bit rate                    : 400 kb/s
Width                       : 1 920 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 16:9
Frame rate mode             : Constant
Frame rate                  : 120.000 FPS
Chroma subsampling          : 4:4:4
Bit depth                   : 8 bits
Scan type                   : Progressive
Bits/(Pixel*Frame)          : 0.002
Stream size                 : 2.81 MiB (98%)
Writing library             : x264 core 161 r3027 4121277
Encoding settings           : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=4 / threads=34 / lookahead_threads=5 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Codec configuration box     : avcC

[Bossett]

Some invesigation - https://bsky.app/profile/bossett.social/post/3l3y5yjp6v22q plays on the phone.

The only difference is chroma subsampling - the new image is 4:2:0 and the original is 4:4:4

mediainfo of working file:

General
Format                      : MPEG-4
Format profile              : Base Media
Codec ID                    : isom (isom/iso2/avc1/mp41)
File size                   : 3.22 MiB
Duration                    : 59 s 0 ms
Overall bit rate            : 457 kb/s
Frame rate                  : 120.000 FPS
Writing application         : Lavf58.64.100

Video
ID                          : 1
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : High@L5.1
Format settings             : CABAC / 4 Ref Frames
Format settings, CABAC      : Yes
Format settings, Reference  : 4 frames
Codec ID                    : avc1
Codec ID/Info               : Advanced Video Coding
Duration                    : 59 s 0 ms
Bit rate                    : 448 kb/s
Width                       : 1 920 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 16:9
Frame rate mode             : Constant
Frame rate                  : 120.000 FPS
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Progressive
Bits/(Pixel*Frame)          : 0.002
Stream size                 : 3.15 MiB (98%)
Writing library             : x264 core 161 r3027 4121277
Encoding settings           : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=34 / lookahead_threads=5 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Codec configuration box     : avcC

working file: https://github.com/user-attachments/assets/5dceff32-53f5-4d08-a303-af45ab1d3c62
generated with: ffmpeg -f lavfi -i testsrc=duration=59:size=1920x1080:rate=120 -pix_fmt yuv420p yuv420p.mp4

suggest the fix here is just to force 4:2:0 in the processing step to maximise compatibility

[Bossett]

https://bsky.app/profile/bossett.social/post/3l3zhoecfp22q - appears now fixed, this is ffmpeg -f lavfi -i testsrc=duration=58:size=1920x1080:rate=120 testsrc5.mp4 and working on iOS