Applying video filter to specific samples of frames.

[Michael Rampe]

[matt kim] “What is the best way to perform a specific video filter on random samples of frames?

At the moment I’ve found that the best way is to just use a -ss command along with the select command of the -vf option.”

This seems like the best way to me as well….

Is there something that you cannot achieve using this method?

Michael

[Matt Kim]

I was just wondering if there is a standard way of achieving this that I am not aware of, because I have just started using FFmpeg.

However, I still wish the -ss option was much faster because at the moment it is not running fast enough as I need to apply this option to thousands of videos.

I am aware that positioning the -ss option before the -i option may allow it to run faster. But it would seem that the videos that I am filtering are unable to do this as well. So at the moment the -ss option runs very slowly–about 1 sec per 1 minute.

Does anyone know of a specific way where I could speed up the execution time of the -ss option?

Thanks,
Matt Kim

[Michael Rampe]

[matt kim] “I am aware that positioning the -ss option before the -i option may allow it to run faster. But it would seem that the videos that I am filtering are unable to do this as well. So at the moment the -ss option runs very slowly–about 1 sec per 1 minute.”

Putting the -ss option before -i skips through the I frames only and is not truly frame accurate. Putting it after the -i decodes every frame to find the exact one you set and is thus much slower.

What is your source codec?

Michael

[Matt Kim]

When I put -ss before -i it starts running the cropdetect filter (i forgot to mention this is what I’m trying to run) at frame 0.

My source codec is H.264