I've consistently used the same footage from my Canon 5D for editing on Vegas for the past years. Everything ran smoothly with Vegas 20. However, after upgrading to Vegas 21 just yesterday, I've been facing a new problem: the video plays as usual, but out of the blue, the video go black and only the audio continues.. cant figure out what is causing that.

Plus vegas 21 is not running smoothly as v20 .. i dont know why they always have problems with the software when they announce a new version.. in the V20 we have updated the software like 3 times in less than 8 months

If you don't give asked information on this user forum it stays your problem without a possibility for help from other users.

I give up!

@j-v what information should i give? i am a vegas user since it was V7 and last year i had the V20 and yesterday upgraded to v21 and i started having the issue that im talking about. Its not related to the footage as i have been using the same videos from canon 5d on vegas 13 till 20 without any problems.
what information you need to help understanding the problem and give solution? may be its something in the software settings i should configure or change?

Can you upload a small size of such media for us to test?

This was the request.

@Nizar-AbuZayyad I asked you to provide a sample so that anyone on this forum can quickly help you solve this simple problem, but no, instead you just kept on complaining.

@Wolfgang S. this is the smallest file size i have for now its 280mb!

1st red flag is the dynamic RAM preview set at 66%, set it back to the default of 5%. Also you have enabled legacy HEVC which will turn off the GPU if your media is HEVC, with DRAM set at 66% Vegas will likely perform poorly. You have a powerful PC which should be great with Vegas so something is adrift with your config/media.

@Nizar-AbuZayyad Hi, that video isn't any good posted on here, you need to share the original,

1. Open Google, top right is a sq of dots - Open Google Drive.
2. Drag that video onto the Google Drive window, let it upload.
3. Right click on the file on screen - Share.
4. A window will pop up, General Access - choose anyone with the link - Copy link.
5. Then on here in a new comment at the top there's a chain button, paste the link on there
6. Click Comment

Anyone from who commented on this post already upgraded to V21?

At least 5 of the posters here, possibly 7 are using 21 based on other posts.

Here's a video that precisely illustrates the issue for clearer understanding. I experimented with various video formats, including mp4 from mobile and GoPro footage, and found that the problem is specific to my Canon 5D's MOV files which never happened on V20. Additionally, there's a slight delay when using keyboard controls for play, stop, or fast-forwarding + the "not responding" thing that happens every while and then for few seconds.. i didnt face such issues with V20. I beleive the issue would be somthing related to settings concerning MOV files but i cant figure out what it is.
@Former user @RogerS @Wolfgang S. @andyrpsmith 

https://drive.google.com/file/d/1qgl_k4rcYWjD8e7cV-5EYEoNiq2pcf0b/view?usp=drivesdk

From my 20+ years video editing experience, my brain says: mov for mac, mp4 for pc.

What if you remux the file to mp4 container? just a tip

@relaxvideo The Canon 5D Mark III saves its video files in the MOV format using MPEG-4 AVC/H
I totally understand your point of view, i have been involved in video editing since 2009. I also used to work on a Mac. However since I started using vegas, I've been using the same 5D camera and its video format without encountering any issues.. please check the video i attached in the previous comment may be there is something wrong with the settings..

Can you show the bottom of preferences/ file io? The video cut it off.

MOV vs MP4 is irrelevant. You could change the extension and it would (usually) still work in VEGAS. Almost all my videos for years were Canon .mov h264 files.

Is it 5DMKII or III? Your posts say both.

Still would be good to have a sample file and sample project to see if others an replicate it. If we can replicate it it's more likely to get solved as a bug; I doubt this is a settings issue (or it wouldn't play at all).

i cannot dl your video with cat - chrome says network error

@RogerS here are more screenshots for the {file io}.. and one more strange thing.. when rendering the footage its playing normal "while rendering" i'm rendering it to Magix AVC/AAC MP4 so its a timeline issue while playing the video and editing, no issues while rendering.

@Nizar-AbuZayyad That 280MB file you uploaded to this site, if that is one of the files you are having problems with upload that to a file sharing site and link it, we can see if it's plays fine

@Former user here it is just uploaded it right now, might take few mins for processing.

https://drive.google.com/file/d/1lIP8jAMWXdmu7fmWoK8EKEpnN8NyxIcf/view?usp=drivesdk