Blackmagic Forum

It seems like no matter what drive I try it on, the wave forms take a while to generate and the disk is only ever running around 80-100MB/s when capable of much faster speeds, tried on multiple different drives.

Did I miss a setting or is this normal? I'm using the mkv container and files around 20gb, I've tried remuxing them to no avail.

Which Resolve version and operating system? Is this on the Edit or Fairlight Timeline?

What is the source media format and codec? What is the source media duration?

Waveforms require some time to build, especially with a lot of media with longer durations.

Is the working folders path local or a network volume?

Version: 19.0.1 Build 6
Timeline: Cut / Edit - doesn't matter where.
Source Media Format: mkv h264 L4.2 / Audio codec: AAC - duration determines how long it takes but for example a four hour video took over 2 minutes to generate the wave form
Working folder path: Local, from a Samsung Evo 970 Plus to a MX500 SSD to a Seagate Barracuda HDD. I've tried them all.

The read speed according to disk activity once dragged onto the timeline or into the cut page is significantly much lower than what's rated on each drive which is which I thought might be a setting somewhere.

Evo 970 Plus: About 110 MB/s (out of 3500MB/s)
MX500: About 80 MB/s (out of 500MB/s)
Seagate Barracuda HDD: About 30 MB/s (out of 200MB/s)

PC Spec and load when putting a new file in (up to 28GB files)
9900K @ 4.7Ghz (8-12% Load)
32GB DDR4 3600Mhz Ram (34% Load)
RTX 3070 (20-30% Load)

My thought that it was caching into the ram as if you delete the entire cache and put the file back in again, the waveform is instantly there again, even after a reload of the program. It's cached into a working folder that you set and the files are tiny, no more than 55mb but it's not deleted under managing the cache from the program you have to do that manually.

I get that it has to read the large video files but I don't understand why the program is reading them so slow in comparison to the read speed of the drive or the hardware assisting it, so I was wondering if I had missed a setting somewhere to speed this up.

A caveat to this is that a friend of mine videos live bands using a bunch of different cameras, puts in 90minute videos that are 40gb and they are near instant. Codec is h264 L5.2. / audio codec: Linear PCM

I just tried with my DJI Osmo Action 4 and that has a codec of h265 L5.0 / audio codec: AAC. The file was 16gb, 20minutes long and very much instant.

So is this a codec issue of the files that come from OBS? Recorded using the nvidia nvenc h264 on the p7 preset, two passes @ 10000Kbps. Is it the video codec decompression the first time davinci reads it just limiting the speed?

Assuming best possible circumstances: Local M2 drive, super fast CPU, then your speed is normal.

I get about 70MB/s reading 4 files for waveform generation, reading from a SSD. I'm limited by my single core CPU speed, so yours are an envy. (23 hours of video took 2 minutes 40 seconds)

Keep in mind that it's not all of the 20GB that Davinci reads, it's only the audio portion of the file.

wave form gen is pretty slow depending on the size of clips you're using, it also won't generate unless you have the track height opened I've noticed

This is a big issue that is REALLY slowing my productivity to a crawl. The time it takes to draw waveforms on longer clips is simply unacceptable in 2024. This is one of the few things about Resolve that has me missing Premiere.

Yeah, it's pretty slow, about 30 seconds per one hour in the timeline for AAC audio.