Terrible Decoder Lag (preview window)

waalkr wrote on 1/27/2024, 11:59 AM

Hello I'm using the newest Vegas 21.0 video software. When trying to edit and simply make cuts in my video I get tremendous lag in the video preview screen. While that happens the application seems to lag as well for a little bit while the decoder is trying to catch up. I have dedicated more ram to the app, I've messed with the File I/O settings and put legacy decoder on which seems to help a bit, but I'm stuck with a product that used to work just fine when I had 16 but just isn't working anymore. I'm running a 2060Super graphics card. Ryzen 7 5800X. and 32gigs of ram. Thank you!

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Former user wrote on 2/3/2024, 5:33 PM

@Reyfox I"m using AMD 5900x, and RTX 4090

Inspected the gop structure and it was 26@250

@Howard-Vigorita Well that's interesting, with the test I did of using Vegas scene detect and rearranging the scenes Vegas should have worked great with an auto GOP of 250, the reason for this is that a new I-frame should be inserted at beginning of each scene, so the first frame after each edit point, and I couldn't work out why Vegas was having such a hard time. It turns out using Shutter encoder on default encoding via NVENC does not do Auto 250, it does a fixed GOP of 250, but using a software encode instead it does invoke Auto 250, with an I-frame on every scene and plays back perfectly.

I don't know why shutter encoder does that. I then used the software encode to edit randomly, this time not on scene change, and it behaves the same as my previous screen recording. With Vegas it needs a very short GOP to edit properly and mostly you get that with camera files, but not distributable files that have longer GOP's for efficiency .

Howard-Vigorita wrote on 2/3/2024, 6:13 PM

I don't usually see issues editing with gops up to 60 or so but 1 (intra) is the easiest. Those longer gops are really for streaming and Vegas seems to be doing Ok lately just playing from the beginning. I don't think the scene detect would put the splits on gop boundaries unless the original encoding software knew where scene splits were and encoded accordingly. Apparently not the case with your clip because the gops were all equal in length: --- GOP histogram : 1 @ 0 : 26 @ 250 [ maxGOPlen=250 ]

Not the case with the one I made either: --- GOP histogram : 1 @ 0 : 221 @ 30 [ maxGOPlen=30 ]

Maybe a Vegas Quantize to Gops setting might be useful.

Former user wrote on 2/3/2024, 7:53 PM

I don't think the scene detect would put the splits on gop boundaries unless the original encoding software knew where scene splits were and encoded accordingly.

@Howard-Vigorita Vegas scene detect is ofcourse splitting on scenes, unrelated to GOP, but Shutter encode on default settings when software encoding uses a GOP of 250, but will reduce that GOP on scene change detect. It makes sense when you think about compression. So when you use auto GOP then use Vegas to split on scene change what you get is a situation where the first frame after the edit point is always an I-frame and Vegas is happier than a pig in mud.

(auto GOP 250)

Apparently not the case with your clip because the gops were all equal in length:

The version I shared was encoded via NVENC, apparently doesn't do auto GOP via Shutterencoder.

Maybe a Vegas Quantize to Gops setting might be useful.

That would interest me, but I'd rather they fix what ever is wrong with the decoder, maybe that necessitates the new render engine that I hope is launching with VP22

RogerS wrote on 2/3/2024, 10:05 PM

Thanks for the insight into ShutterEncoder, I didn't know about auto GOP.

I look forward to continue to test VEGAS's decoder/video engine as it evolves through 21 and beyond.

fr0sty wrote on 2/3/2024, 10:13 PM

That would interest me, but I'd rather they fix what ever is wrong with the decoder, maybe that necessitates the new render engine that I hope is launching with VP22

Because a new video engine rebuild is a long and complex process that could take a long time to complete, it likely isn't going to launch all at once, but rather in pieces... some of those pieces may come sooner than you think.

Howard-Vigorita wrote on 2/4/2024, 10:13 AM

... I'd rather they fix what ever is wrong with the decoder, maybe that necessitates the new render engine that I hope is launching with VP22

@Former user Only added gop behavior that I would find useful would be an option for Vegas to close gops on rendering at clip splits. Or an option to set an overriding gop size-limit on renders. But I wouldn't choose those options unless I were rendering an intermediate. The Shutter Encoder default makes sense to me only for uploads to streaming sites like YouTube. Open gop would be even better. But long gops are the worst choice for editing. I would want to change the default if that's the way I used it.