#799 When using SelectEven() to halve framerate, original framerate is used when muxing to mp4 (standard or m4v)

[Eli Bildirici]

I deinterlaced a video with QTGMC and then used SelectEven() to halve the framerate. The resulting file, however, was still at the doubled framerate output of QTGMC. However, according to the log, the problem isn't with the encode itself - it's that, when selecting mp4 format output, for some reason the doubled framerate is passed as a parameter to mp4box. I'm not sure how exactly this happens, but it definitely does. Even if fps is set explicitly as a parameter for x264, MeGUI doesn't make use of that information to supply the correct fps to mp4box. I've confirmed that this only happens with mp4 output, not rawavc or mkv. So either the settings for mp4box need to be given a place in the UI directly, or this behavior just needs to be fixed.
I'm going to look to see if this is something I can fix myself but thought that everyone should be made aware.

[Eli Bildirici]

To be clear - SelectEven() did its work, but the file was then played back at the original fps. Not good :(

[Zathor]

Thanks for the report. I assume you created first an encode with QTGMC and then this file has been encoded again with selecteven(), correct? I try currently to reproduce the problem. If possible please upload a log file.

[Eli Bildirici]

Eh it was the same filter chain, there was no intermediate encode. So: source filter, QTGMC, sharpen, dehalo, and finally SelectEven(). I know this is not efficient but I wasn't sure if there would be any detrimental effects on the other filters by calling SelectEven() first.
The job was a while ago so it'll take me a bit to find the log for it. If I can't find it quickly, I'll probably just try to reproduce it and post that log here.

ED: NVM, I found it. It is clear that 59.940 fps is passed to mp4box (line 153, 157) even though the encode is at 30000/1001 and MediaInfo confirms that the resulting intermediate 264 file is at 30000/1001. Very weird. [Removed Dropbox link]

[Zathor]

I have downloaded the sample file. Thanks.
How did you create the avs file in the log? File indexer, then avs script creator, save & queue the video? I am asking as the frame rate of the initial video must have passed to mp4box and need to find from where. I can try all alternatives mayself but it would be good to have a starting point.

[Eli Bildirici]

I used File Indexer to create the d2v and demux the audio, and then wrote the avs myself (without using the script creator, according to a template I'm using for all my X-Men encodes). Then just selected it in the main UI and hit queue. I'm as confused as you as to where mp4box got 'OriginalFrameRate' from. It's not in the x264 params, and the original d2v is of course 30000/1001 interlaced.

[Eli Bildirici]

I'll try to find the time to reproduce this as well...

[Zathor]

Ok, found the problematic area. The FPS will be checked and fixed when you "queue" the encode. If you change the avs afterwards the FPS will be wrong. Also if the video preview is disabled it will be set to 0.

I will change it so that directly in the mux step the fps is derived from the mediainfo information of the video file. Only option to force it will be the mux dialogue (which is also getting the information from mediainfo but it can be changed for muxers != AVI).

[Zathor]

fixed in 2548

[Eli Bildirici]

Cool! Glad you figured this silly little thing out. (I did in fact have the video preview disabled.)