All of my tests so far have been with ffmpeg 4.1.1. I noticed a lot of “avformat/matroskadec” items in the change log for 4.2, so I got the new version, rebuilt 50 minute transcodes of the original video, and redid all my tests using 4.2. There was no change or improvement of any kind.
Yes, direct and complete transcode of a source file straight from a mirrorless camera.
True. But on a practical and observable level, load and seek times are sub-second on a 50-minute AVI file using Ut Video or HuffYUV regardless of where the -ss is located. It is just MKV that is slower.
While -ss before -i is clearly doing more computational work, it isn’t 40 seconds worth.
I don’t know the answer to this, but I can say that MPC-BE Media Player is able to instantly load and seek a 50-minute MKV file made by ffmpeg. This tells me the ffmpeg encoder and the Matroska format are fine. It is the ffmpeg decoder dropping the ball. My understanding is that MPC-BE has its own decoder for many formats, so it’s hard to know if it’s using ffmpeg for decoding or not.
This is my guess. The file size difference between MOV-in-Matroska and straight MOV is measured in mere bytes. My understanding is that Matroska is a (should be) lightweight wrapper around a normal MOV file. I would expect MOV to play just as fast as something native like WebM, and indeed it does with MPE-BE as I’ve recently discovered.
This would be a great test. But I’m not familiar with the tool, and I already know the MKV file is fine now that I’ve seen MPC-BE play it, so I will save this test for later. I think there’s enough evidence to point to the ffmpeg decoder now.
Your post was the first I had heard of it. A quick look around, and it seems like an incredible codec. I’m not sure I have a way to add it to my workflow, but I’ll keep an eager eye out for it.
Thanks pdr for helping narrow down the problems here. I think I have enough information to write a bug report to the ffmpeg team. The good news is that Matroska should work in theory since MPC-BE can play it. If we can get Shotcut to the same speed via a patched ffmpeg, we regain all our favorite lossless codecs with full color space and color range metadata.
I provided a little background about that in the second post of this thread. One video with FLAC may not cause Shotcut to stutter, but multiple videos doing a transition will produce way more load on your CPU than necessary.