QP file output

[tormento]

x265 (and other software) accepts a .qp file to force a frame type to be applied to a certain frame.

An example is:

0 I -1
1640 I -1
3789 I -1
17191 I -1
31784 I -1
33927 I -1

to have proper scene change cuts.

Here you can find the syntax.

It can be derived by chapters but it's almost of no use when wanting a clean cut frame per each scene.

Would you mind to add that kind of output?

[Breakthrough]

Thanks, this falls under some of the other open issues to expand on output formats. I think we should add a new command like export-scenes that is dedicated for this purpose, so that the cuts can be saved in various formats. Updated #344 to include a link to this issue.

I would imagine the command to look something like export-scenes -o "cuts.qp" and have the format auto-detected from extension where possible, or explicitly specified with another flag. We could also allow specifying export-scenes several times to generate the output in different formats.

[tormento]

Thanks, do you have any ETA?

[Breakthrough]

Unfortunately no ETA at this time, but in v0.6.3 you can now generate a list of cuts as frame numbers instead of timecodes with a config file. To do this, you can add the following to a config file:

[list-scenes]
cut-format = frames

And then use the list-scenes command to generate a CSV file, the first row will be the frames that you need to add I frames for. So the row would contain the following from your example:

1640,3789,17191,31784,33927

You might be able to wrangle that into a QP file with some bash magic or write a small Python script. If you're using the Python API, the detect function should already return the info you need.

[tormento]

Excel can do magic tricks ;)

[tormento]

Tried your release, sorry for the delay.

It works ok but the generated CSV is not properly "standard".

I mean: looking at the file, we have a first part with Timecode list and a second part with Scene Number, that are CSV formatted in a really different way each other.

Please, write two files so that I can directly import the Scene number and frame in Excel.

When you will have time (if you want to ease my CSV file "postprocessing" :) ), simply output a file with a column of plain scene start frames, almost such as the example I did in the first post.

[Breakthrough]

@tormento if you use the --skip-cuts option the file will omit the first row to allow it to be imported directly into Excel. This is not done by default for historical reasons, and will be fixed when we have a replacement for the list-scenes command in a future version.

The start frame column should align with the cut points you need for I frames.

[Breakthrough]

@tormento one thing I'm not totally clear on is how this works with input seeking. Do the frame numbers refer to the encoded output frame numbers, or the frame numbers of the input?

For example, if we use start seeking, does the QP need to still start from frame 0, or should it be shifted?

[tormento]

The QP file tells the encoder (x264/x265) where to force a specific type of frame.

In our case, to have a clean scene cut, we need I type, i.e. what once was called a keyframe.

The CSV that PySceneDetect is shifted by 1, compared to encoder convention (wheree first frame is 0), so you need to take the (Start Frame-1) to have the appropriate position.

P.S: I think that the -1 value is totally optional but some tools output it and I kept on using. According to x265 readme, the number after the frame type should force a QP value but I never had use of it other than for keyframes.

[Breakthrough]

@tormento Thanks, I should have that working now as a new save-qp command. Would you like to test a development version to verify? You can grab one for Windows here or from the latest build on PR #427. Replaced by PR #448

Invoking it as scenedetect -i video.mp4 save-qp results in the following example video.qp:

0 I -1
90 I -1
210 I -1

Let me know what you think :)

[tormento]

Will try ASAP.

[tormento]

Works perfectly, same result as my manual csv to qp conversion.

Thank you! You saved me a lot of work!