FFmpeg: Improve performance by seeking input rather than output video

[alexspurling]

This improves performance when converting video to images as we no longer have to decode and then discard the first x seconds of video.

The current code creates an ffmpeg command like this:

/usr/bin/ffmpeg -y -i /go/src/github.com/photoprism/photoprism/storage/originals/2023/01/20230130_101623_A472124D.mp4 -ss 00:00:30.000 -vframes 1 /go/src/github.com/photoprism/photoprism/storage/sidecar/2023/01/20230130_101623_A472124D.mp4.jpg

This tells ffmpeg to decode the first 30s of the input before extracting a frame and writing it as a jpg.

This pull request changes the ffmpeg command to:

/usr/bin/ffmpeg -y -ss 00:00:30.000 -i /go/src/github.com/photoprism/photoprism/storage/originals/2023/01/20230130_101623_A472124D.mp4 -vframes 1 /go/src/github.com/photoprism/photoprism/storage/sidecar/2023/01/20230130_101623_A472124D.mp4.jpg

This tells ffmpeg to efficiently seek to the desired frame, write the jpg and then exit. This results in a significant speed up when importing large video files.

Log file before:

2023-11-19 10:15:27 INFO upload has been processed
2023-11-19 10:15:27 INFO upload: imported 2 files
2023-11-19 10:15:27 INFO upload: deleted empty folder /go/src/github.com/photoprism/photoprism/storage/users/us4d78b290vwb8x0/upload/sessk1toutkldiu6jt
2023-11-19 10:15:27 WARN import: 2023/01/20230130_101623_A472124D.mp4 exceeds file size limit (2.8 GB / 1.0 GB)
2023-11-19 10:15:27 INFO media: created 11 thumbnails for 2023/01/20230130_101623_A472124D.mp4.jpg [428.211754ms]
2023-11-19 10:15:27 INFO convert: 20230130_101623_A472124D.mp4.jpg created in 9.770663681s (ffmpeg)
2023-11-19 10:15:17 INFO convert: converting 20230130_101623_A472124D.mp4 to 20230130_101623_A472124D.mp4.jpg (ffmpeg)
2023-11-19 10:15:09 INFO import: moving main mp4 file P1870007.MP4 to 2023/01/20230130_101623_A472124D.mp4
2023-11-19 10:15:02 INFO media: P1870007.MP4 was taken at 2023-01-30 10:16:23.337 +0000 UTC (meta)

Log file after:

2023-11-19 10:32:39 INFO upload has been processed
2023-11-19 10:32:39 INFO upload: imported 2 files
2023-11-19 10:32:39 INFO upload: deleted empty folder /go/src/github.com/photoprism/photoprism/storage/users/us4d78b290vwb8x0/upload/sessk1toutkliytixjf
2023-11-19 10:32:39 WARN import: 2023/01/20230130_101623_A472124D.mp4 exceeds file size limit (2.8 GB / 1.0 GB)
2023-11-19 10:32:39 INFO media: created 11 thumbnails for 2023/01/20230130_101623_A472124D.mp4.jpg [461.212762ms]
2023-11-19 10:32:38 INFO convert: 20230130_101623_A472124D.mp4.jpg created in 707.282911ms (ffmpeg)
2023-11-19 10:32:38 INFO convert: converting 20230130_101623_A472124D.mp4 to 20230130_101623_A472124D.mp4.jpg (ffmpeg)
2023-11-19 10:32:30 INFO import: moving main mp4 file P1870007.MP4 to 2023/01/20230130_101623_A472124D.mp4
2023-11-19 10:32:24 INFO media: P1870007.MP4 was taken at 2023-01-30 10:16:23.337 +0000 UTC (meta)

Acceptance Criteria:

• Features and enhancements must be fully implemented so that they can be released at any time without additional work
• Automated unit and/or acceptance tests are mandatory to ensure the changes work as expected and to reduce repetitive manual work
• Frontend components must be responsive to work and look properly on phones, tablets, and desktop computers; you must have tested them on all major browsers and different devices
• Documentation and translation updates should be provided if needed
• In case you submit database-related changes, they must be tested and compatible with SQLite 3 and MariaDB 10.5.12+

[CLAassistant]

All committers have signed the CLA.

[lastzero]

Excellent! I wasn't aware that changing the parameter order helps in this case.

[lastzero]

An updated development preview build is available for testing:

• https://docs.photoprism.app/release-notes/#development-preview
• https://docs.photoprism.app/getting-started/updates/#development-preview

[lastzero]

@alexspurling I've tested it with a few large videos and it seems to be much faster now. Thank you very much! ❤️

[srett]

FWIW (but I don't think it really matters here), this makes the seek less accurate, as ffmpeg can only seek to the beginning of a GOP when not decoding, so you usually end up a few seconds before the desired timestamp... OTOH, this means we end up on an I-frame, which usually has slightly better quality.

[lastzero]

FWIW (but I don't think it really matters here), this makes the seek less accurate, as ffmpeg can only seek to the beginning of a GOP when not decoding, so you usually end up a few seconds before the desired timestamp...

We value your feedback and insight! Happy to implement further improvements if needed.

OTOH, this means we end up on an I-frame, which usually has slightly better quality.

I agree, that's actually an advantage, as time accuracy is not important for this use case.