Fix some media attachments being converted with too high framerates #17619
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Video files with variable framerates are converted to constant framerate videos and the output framerate picked by ffmpeg is based on the original file's container framerate (which can be different from the average framerate). This means that an input video with variable framerate with about 30 frames per second on average, but a maximum of 120 fps will be converted to a constant 120 fps file, which won't be processed by other Mastodon servers. This commit changes it so that input files with VFR and a maximum framerate above the framerate threshold are converted to VFR files with the maximum frame rate enforced.
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To be honest, I would advocate changing the flags to switch to variable framerate unconditionally, as I see no reason to stick to CBR with x264 MP4 files… for the record, we have used this flag since 6382ef2, when Mastodon used to encode to WebM. No rationale has been given in that commit, and I wasn't around in the project at that time, so I don't know what was the reason for that choice. I suppose this may have been linked to https://bugzilla.mozilla.org/show_bug.cgi?id=1022762 In the meantime, this PR is conservative in its approach by only changing the options if the file has a max framerate that exceeds the framerate limit, which means it should only change how files that currently cause issues are processed. |
Gargron
approved these changes
Feb 22, 2022
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Video files with variable framerates are converted to constant framerate videos and the output framerate picked by ffmpeg is based on the original file's container framerate (which can be different from the average framerate).
This means that an input video with variable framerate with about 30 frames per second on average, but a maximum of 120 fps will be converted to a constant 120 fps file, which won't be processed by other Mastodon servers.
This commit changes it so that input files with VFR and a maximum framerate above the framerate threshold are converted to VFR files with the maximum frame rate enforced.