Weird render artifacts

DWPhoto wrote on 9/15/2014, 12:54 AM
Hi All

I could really use some help with this one.
I've been doing some instructional videos for a little while now and rendering an mp4 via Mainconcept AVA/AAC., at around 1750000 bitrate

Everything was fine until a big pc crash and rebuild. Now when I export with the exact same settings as before, I get a pulsing pixelation in the final render. I don't even see this the low res preview when editing.
I can't for the life of me work out what's different to before or how to fix this.
here is a sample to see what I mean:
http://dwphoto.smugmug.com/Deans-Misc-Stuff/Misc/i-S9xv5GJ

Any help would be very much appreciated

By the way, how do I embed video for a post ?

Comments

OldSmoke wrote on 9/15/2014, 9:26 AM
I am not sure what your link is supposed to show; surgery?

Have you by any chance GPU acceleration ON in both, the preferences and your render template? If so, try switching it off. This all depends on your system but you don't have your system specs up so its hard to tell.

To post a video follow the instructions under a stick called New Forum Markup.

Proud owner of Sony Vegas Pro 7, 8, 9, 10, 11, 12 & 13 and now Magix VP15&16.

System Spec.:
Motherboard: ASUS X299 Prime-A

Ram: G.Skill 4x8GB DDR4 2666 XMP

CPU: i7-9800x @ 4.6GHz (custom water cooling system)
GPU: 1x AMD Vega Pro Frontier Edition (water cooled)
Hard drives: System Samsung 970Pro NVME, AV-Projects 1TB (4x Intel P7600 512GB VROC), 4x 2.5" Hotswap bays, 1x 3.5" Hotswap Bay, 1x LG BluRay Burner

PSU: Corsair 1200W
Monitor: 2x Dell Ultrasharp U2713HM (2560x1440)

larry-peter wrote on 9/15/2014, 10:19 AM
Is the pulsing pixelation you're seeing something like - clean frame, several frames of pixelation, clean frame, etc.? You may be seeing visible differences between the i-frames and the compressed frames between them. That would indicate you need to increase the bitrate of your render.

I would check your rendered file in MediaInfo to see if the actual bitrate reflects the setting in the render template.
DWPhoto wrote on 9/15/2014, 6:54 PM
The footage is actually waxing instruction for a diploma of beauty course.

My system is an Intel i7 860 @ 2.8GHz, 16gb ram, win 7 64 bit, gforce GTS250

I've tried your suggestion but it didn't seem to make any difference

DWPhoto wrote on 9/15/2014, 7:04 PM
"Is the pulsing pixelation you're seeing something like - clean frame, several frames of pixelation, clean frame, etc.? You may be seeing visible differences between the i-frames and the compressed frames between them. That would indicate you need to increase the bitrate of your render.

I would check your rendered file in MediaInfo to see if the actual bitrate reflects the setting in the render template. "


The weirdest thing is that earlier renders came out fine at the current bitrate. Even weirder, I just re-rendered some older footage with my current profile and it came out fine, no weird artifacts. And when I check the file properties of this against the one I'm having trouble with - they are identical.

I can't understand this at all - how is that possible ? Same cameras, same project settings, same render profile - but 2 different results
astar wrote on 9/15/2014, 11:03 PM
This is really hard to determine based on the info provided, even the photo.

Have you tried using Sony AVC, or have you tried exporting to say something like DV or XDCAM.MP4, and see if you see the same issues? If you do not see the issues with those codecs, try using Handbrake on the DV or XDCAM, and see if you have the same issues with player playback.

Just some thoughts.
John_Cline wrote on 9/16/2014, 2:01 AM
Determining bit rate versus desired image quality is an art. If the video is noise-free, has relatively little detail and the entire frame isn't filled with fast motion, then you can get away with a very low encoding bit rate and still have a good looking video, of course, image size and frame rate also factor into the equation. In your case, the video appears to be noise-free and I'm assuming there isn't a lot of motion, where the problem seems to be is the detail in the terrycloth towel. This is likely going to require a higher bit rate than 1,750,000 bps.
DWPhoto wrote on 9/16/2014, 3:22 AM
I just realised my link I posted wasnt to the actual video.
I've now linked to the video - particularly the end part of it is the worst.
I'm not very familiar with other export formats. I just know that what once worked perfectly now sucks big time
John_Cline wrote on 9/16/2014, 3:51 AM
Exactly what parameters did you use to encode the video?

Encoding is not a "one size fits all" procedure. If you really need a low bit rate for streaming from a web server, Handbrake does a much better job.
john_dennis wrote on 9/16/2014, 8:40 AM
"[I]Everything was fine until a big pc crash and rebuild.[/I]"

When Vegas is first loaded, the render template encode mode for GPU rendering is set to Automatic. Try using CPU Only.

Also, even though you were happy before the crash, this might make interesting reading.
OldSmoke wrote on 9/16/2014, 9:03 AM
[I]When Vegas is first loaded, the render template encode mode for GPU rendering is set to Automatic. Try using CPU Only.[/I]

Well I asked about that before but there was no answer; maybe we get one this time.

Proud owner of Sony Vegas Pro 7, 8, 9, 10, 11, 12 & 13 and now Magix VP15&16.

System Spec.:
Motherboard: ASUS X299 Prime-A

Ram: G.Skill 4x8GB DDR4 2666 XMP

CPU: i7-9800x @ 4.6GHz (custom water cooling system)
GPU: 1x AMD Vega Pro Frontier Edition (water cooled)
Hard drives: System Samsung 970Pro NVME, AV-Projects 1TB (4x Intel P7600 512GB VROC), 4x 2.5" Hotswap bays, 1x 3.5" Hotswap Bay, 1x LG BluRay Burner

PSU: Corsair 1200W
Monitor: 2x Dell Ultrasharp U2713HM (2560x1440)

musicvid10 wrote on 9/16/2014, 10:05 AM
I just looked at the video.
At least in that render (postprocessed by Smugmug??), there is no mystery whatsoever in my mind.
Artifacting from minimum bitrate being too low; nothing else that I can see. Try Handbrake, and if you still get the blocking, I can show you how to raise vbv-min.

That said, I have no earthly idea why things changed after a system crash; did you by chance lose a template you "had" been using?

More analysis is possible if you'll upload the original rendered clip to a fileshare like Dropbox, Mediafire, or Google Drive. I don't seem to be able to download the original from your smugmug page.
johnmeyer wrote on 9/16/2014, 2:38 PM
Since the OP hasn't provided many details about the render settings, let me try it the other way around, and suggest some settings.

First of all, as musicvid just said, a higher bitrate is a really good idea. I'd suggest trying at least 4,000,000 bps, but you can certainly use higher values.

Second, here are the settings I'd use. I've shown your 1,500,000 bps. In addition, don't forget to set the quality to "Best," since you'll probably be re-sizing.



Please note that there is an interaction between "Frame Size" and bitrate. As you increase the frame size, you also must increase the bitrate in order to get the same spatial quality. For instance, if you were to use the exact same settings shown here, but instead encoded to 1920x1080, you would get far more pixelization and other artifacts. Since most streaming sites do a much better job with 720p than 1080i or 1080p, you are generally much better off sticking with this lower resolution.

Using Main instead of Baseline for the profile should also improve the quality. We just had a discussion about this, and while I don't think we ever came to any definitive conclusions, it is still my belief that for a given bitrate, you will get better results when using the higher profile. However, it will require more CPU power to decode that file. I don't think that will matter for your application.

I set the max bitrate a little too high before I did my snapshot. You probably don't need to set it any higher than 2-3x the average bitrate.

I didn't make any comments about setting the frame rate, but you definitely want to set so that it matches the frame rate of your original video.



DWPhoto wrote on 9/23/2014, 3:25 PM
Thanks to everyone who responded to my question. I ended up using a much higher bit rate which fixed the problem, but did give me a much bigger file.
We changed from embedding the videos in the learning modules, to having them streamed from Vimeo, so the size was as crucial as before.
I still don't know why things changed after my pc crash, but I'm not going to obsess over it given we now have a workable solution.
Interestingly when I rendered 35 or so final videos, Vegas didn't crash once. A minor miracle in itself .... :)