Low encoding performance depending on input method with filter complex

[daneelveloper]

For testing video encoding performance (audio is negligible) I'm using command line ffmpeg.exe (4.0.2) and a single video clip. 1920x1080, 29.97 fps, h264 video, aac audio 48000khz stereo.

The following command encodes at an average 4.5x speed:

ffmpeg -i input.mp4 -filter_complex "negate" -c:v mpeg4 -y output.mpeg

But the next command only gets to 1.7x speed:

ffmpeg -filter_complex "movie=input.mp4,negate" -c:v mpeg4 -y output.mpeg

The difference is quite remarkable considering both are basically the same process. Maybe movie filter could be improved to speed encoding up.

Thank you.

[Marton Balint]

The movie source does not set the thread count to auto, therefore it uses a single threaded video decoder.

[daneelveloper]

Let me add that split filter derived sources seems to be also single threaded. It be great if both input methods could be multithreaded as -i ones.

[Elon Musk]

Can you please give example for split filter?

[daneelveloper]

In this examples I'm splitting the input clip (1920x1080, 29.97 fps, h264 video, aac audio 48000khz stereo. Audio negligible) into two separate inputs.

Speed values as reported by ffmpeg.exe (4.0.2)

This one runs at 4.15x speed.

ffmpeg -i input.mp4 -filter_complex "split[v0][v1],[v0][v1]blend=extremity" -c:v mpeg4 -y output.mp4

And the next just goes up to 1.65x speed.

ffmpeg -filter_complex "movie=input.mp4,split[v0][v1];[v0][v1]blend=extremity" -c:v mpeg4 -y output.mp4

In the second example it's obvious the slowness comes from movie filter but it also states that split filter derived inputs won't improve speed.

Thank you.

[Elon Musk]

Sorry, but how split filter could improve speed over movie slowness?

[daneelveloper]

Replying to richardpl:

Sorry, but how split filter could improve speed over movie slowness?

As you point out, I agree it seems split filter is not a bottleneck but the non-optimized operation of movie filter source compared to -i input alternative.

[Carl Eugen Hoyos]

Should be fixed in 7ffa458d600eccbd2582d755af75c03bdaa9e51f