avisynth or ffmpeg massive slowdown on one particular file

[bakonfreek]

LWLibavVideoSource("C:\~\00001.MTS")
AssumeTFF()
QTGMC(Preset="Slower")
prefetch(32)

I have to be missing something.

Yes, I am well aware the preset is called "slower", but on every other video in the directory (they're all videos off my old AVCHD camcorder from high school like 12 years ago), the encode will generally run at between 75-85 fps. This one video in particular though, well, you can see the screenshots, it's pulling half a frame per second and falling. It starts off zip quick, but then it just, I dunno, poops its pants or something.

The script is the same for every video in the folder and the ffmpeg input is the same for every video in the folder, with differences for the specified inputs and (in ffmpeg) output file names.

[ProWo]

The second video stream #1 input should not exist.

[poisondeathray]

post the command line used

[bakonfreek]

As stated earlier, the previous video (00000.avs/00000.MTS) went along fine at between 75-85fps with everything else remaining the same other than the input/output file names being different.

Regarding the bitrate, I have my reasons for needing that, but again, the previous file (and other unrelated files) did not see this amount of slowdown (maybe I could make LSMASH decode with the GPU as well since apparently it will do that, I dunno, dumping encode duties on the GPU and having a ridiculous amount of threads for the rest of the script to prefetch with seems to have a significant speedup with everything else).

Of note as well, I did work around this (today, like 30 minutes ago, 21 November 2024) by converting the MTS files to HEVC, which should be more difficult for my CPU (LSMASH) to work with regarding decoding duties, but now everything runs along at ~100fps? Same avs script. I'm confused, but I'll take that result even if it does require extra steps. Same ffmpeg input as well, except the second input is "00001.MP4" since I'm using my reencoded go-between HEVC file to "yoink" the audio from when I spit out deinterlaced video.


[Attachment 83635 - Click to enlarge]

[_Al_]

You have second ffmpeg input set even in your first example though, as was pointed out. But no command line available, as was pointed out as well. So why are you expecting any answer?

[beyonslay]

You can check the integrity of the video using ffmpeg -v error -i video.mp4 -f null - to see if there are any errors or warnings in the decoding process.

snaptube vidmate

[hello_hello]

How old is the version of QTGMC you're using? And I guess the same question applies to the plugins it uses.
I ask, as it sounds much like a problem I (and some others) experienced with QTGMC years ago, when some encodes would start off at normal speed and gradually slow to a crawl. I don't think the exact cause was ever determined. It was possibly a combination of plugins.
https://forum.doom9.org/showthread.php?t=172744

If you happen to have avstp.dll auto-loading you should get rid of it as it can cause problems with Avisynth's own multi-threading.

Even if they're up to date, I'd recommend trying the dogway version of QTGMC. It's a little faster than the standard version and the quality seems to be a little better.
https://github.com/Dogway/Avisynth-Scripts/blob/master/MIX%20mods/QTGMC%2B.avsi
It also supports using a GPU for some of the processing. It requires a couple of other dogway functions, listed at the top of the script. Using it without GPU processing, if necessary, would look like this:

QTGMCp(Preset="Slower", gpuid=-1)

As dogway's version is named QTGMCp it can co-exist with an older version.