Long AVCHD video files are causing hanging issues in premiere pro

[Piers27993239ra3u]

So I'm going to preface this by saying that I do multi track editing in a weird way; I layer all the video files, and then cut down through the layers to show different camera angles. On a project I'm currently working on I have an .mts file as the bottom layer (avchd), and 3 mp4 files above that. Recently Premiere pro has started exhibiting strange behaviour when playing back the long mts / avchd file. If I make a cut or make any change to the mts video file, premiere hangs and appears to be reindexing the video file. During this time the play button doesn't work - and worse, if playback is mid progress, I'm then unable to stop playback until it's finished reindexing the file. This slow down results in very lengthy edit times.

This wasn't a problem until one of the more recent updates. Using disk management, you can see premiere pro maxing out the USB hard drive's transfer speed trying to re-read the entire video file which I'm trying to work on. Toggling visibility on the layer containing the mts file fixes the issue, but while this does speed up the progress until I need that layer, it doesn't get around the fact that premiere pro still can't seem to handle avchd/mts files at the moment.

Unfortunately I'm unable to share footage as it's of a sensitive nature with child protection and blurring needing to be done on the finished product.

The file in question is from a sony handycam, 1080p 50fps, 24mb/s 256kbs audio, 1hr 3 mins in length and about 11.8gb

Any insight on this would be appreciated as almost all of my multicam projects use MTS files for at least one of the cameras.

[Piers27993239ra3u]

I forgot to add, I'm on a Dell XPS 9560 (quite old now) Windows 10, premiere pro 25.3.0

[Rach McIntire]

Hi @Piers27993239ra3u,

Welcome to the Premiere Pro forums! We’re happy you’ve reached out. I'm sorry to hear you're having issues with MTS files. 
I am aware of a recent MTS files issue, but it doesn't sound similar to what you're experiencing. Would you happen to know what version you were on previously and where it was playing smoothly?  Do you know how to capture a DMP file from Task Manager?  If so, please feel free to send that along.  Your computer is definitely on the older end.  Keep an eye on our Minimum and recommended system requirements.  

Are any background features like automatic subtitles or audio tags turned on?  I would also make sure your graphics driver is up to date.  If you have time, please see, How do I report a Problem? to give us more details.  I hope we can help you soon.

[R Neil Haugen]

You mention this is on a USB connected drive, is that correct?

If the file is on an internal drive, do you get the same error?

[Piers27993239ra3u]

@Rach McIntire 
I've just checked me laptop specs are they are above the minimum recommended.
Intel i7-7700HQ @ 2.8ghz (4 cores / 8 threads)
32gb ram
4k monitor
Intel HD Graphics 630
Nvidia GTX 1050 with 4gb dedicated vram

I turned off automatic subtitling and audio tags when I first got updated to v25 as it wasn't needed for my projects and was really slowing down importing of any large files.

Other video files including newer mp4 files appear to run fine. Unfortuantely I'm not entirely sure when the problem first arose, I think I became aware of it after upgrading to v25 from v24 but I've not been working with mts files recently enough to notice it until I opened one of the projects today.

I have just created a dump file for premiere pro, however it's 12gb in size so I'm not sure if it's sensible to upload as my internet isn't the fastest.

@R Neil Haugen  Yes the file is on an external SSD connected via USB 3.2 with a throughput of about 300mb/s which is ample for this project. I have edited up to 9 layers of video including 2x 4k files without issue from this USB hard drive. I can certainly give it a go copying it onto the main hard drive to see if it helps, however I'm not sure if I'll see a change as this seems to be very much codec dependent as opposed to hard drive related (all the other files for the project are on the same hard drive and premiere pro has no issue with those).