Uploading to YouTube to get the best quality: Resolution, bitrate and whatnot

[WILSONEUC]

I edit all my content through Davinci Resolve Studio - Paid. I try to work with all 4K content now from go pro hero 8 , insta360 (processed through the studio as 3840x2160 h265, full bit rate render) ,mavic air 2 drone. Project setting at start is edited in 3840 × 2160, including timeline , full data levels. I produce the video  3840 × 2160 as a .mp4 file, h264 with a bitrate 30000, network optimized and i leave the rest default. I also render the video with my 1070 and not from my cpu.

Most 10 minute video renders process through my 1070 take about 4 minutes

Youtube takes about 1 hour to upload the 10 minute video file, 30 minutes to make the video show in 1080p and 2 hours for 4K. It is best i can  do with my internet speed and not sacrifice too much quality from the original footage. 

 

Edited September 28, 2020 by WILSON-YT

[btl]

Hi @ all,

i uploaded a video to YT and it just looks incredible poor on the riding scene, can't get it look OK. I'd be open for hints :-)

Camera is my Insta360 One X, i exported the flat video from Insta Studio in 1440p 25 FPS with maximum Bitrate and cut the scenes in VSDC or Adobe Premiere Elements 2021.

The exported video looks good (as good as autumn video gets with that low light) in VLC, but uploaded to YT its literally unwatchable. I tried many different settings, even faked 50fps / CBR / VBR 2-pass / 4k Ultra presets. but none of the videos are watchable quality after YT upload.

I uploaded a short clip of my video without re-encoding, directly from my Insta360 studio to youtube ( https://www.youtube.com/watch?v=uxcKupRMhX8 ) and also to my google drive ( https://drive.google.com/file/d/18NRnpYUhljy3cYRhWVUSWBlNRJejq1oS/view?usp=sharing ) , so you can see the source quality. 

Is someone able to render this properly and upload it to YT in a quality that deserves the "HD" logo? 

 

Thanks, 

Stefan

 

[ZenRyder]

11 hours ago, btl said:

Hi @ all,

i uploaded a video to YT and it just looks incredible poor on the riding scene, can't get it look OK. I'd be open for hints :-)

Camera is my Insta360 One X, i exported the flat video from Insta Studio in 1440p 25 FPS with maximum Bitrate and cut the scenes in VSDC or Adobe Premiere Elements 2021.

The exported video looks good (as good as autumn video gets with that low light) in VLC, but uploaded to YT its literally unwatchable. I tried many different settings, even faked 50fps / CBR / VBR 2-pass / 4k Ultra presets. but none of the videos are watchable quality after YT upload.

I uploaded a short clip of my video without re-encoding, directly from my Insta360 studio to youtube ( https://www.youtube.com/watch?v=uxcKupRMhX8 ) and also to my google drive ( https://drive.google.com/file/d/18NRnpYUhljy3cYRhWVUSWBlNRJejq1oS/view?usp=sharing ) , so you can see the source quality. 

Is someone able to render this properly and upload it to YT in a quality that deserves the "HD" logo? 

Thanks, 

Stefan

 

As you can see, the stats look correct on YouTube. You've got the vp09 Codec, so honestly, you can't do better than that from the YouTube standpoint.

I looked at the same video on the Google share and it seems to be similar in quality.

So, I'm not sure what the complaint it. The video does have low light. Realize that 360 video is 5.7k in full 360. When you reframe it, there is much less video to actually use than 5.7k unless you are doing a fish eye view which is not very watchable. When you export in 2k (2560x1440) Insta360Studio is filling in the bits and trying to upscale it with various degrees of success. We know that you're not going to get incredible 2k output, but we're doing it to gain the vp09 codec that YouTube uses which improves the end result quality dramatically in most cases. However, if the original footage is dark or doesn't have a lot of image detail, there is not much it can do. 

I would try again and capture some footage on a sunny day and compare the output. 

This is captured on an Insta360 One R (5.7k), reframed in 2k, uploaded to YouTube.

 

[btl]

Quote

As you can see, the stats look correct on YouTube. You've got the vp09 Codec, so honestly, you can't do better than that from the YouTube standpoint.

I looked at the same video on the Google share and it seems to be similar in quality.

So, I'm not sure what the complaint it. The video does have low light. Realize that 360 video is 5.7k in full 360. When you reframe it, there is much less video to actually use than 5.7k unless you are doing a fish eye view which is not very watchable. When you export in 2k (2560x1440) Insta360Studio is filling in the bits and trying to upscale it with various degrees of success. We know that you're not going to get incredible 2k output, but we're doing it to gain the vp09 codec that YouTube uses which improves the end result quality dramatically in most cases. However, if the original footage is dark or doesn't have a lot of image detail, there is not much it can do. 

Sure, i know a 16:9 reframe out of an 5.7k 360° video will hardly have enough detail for a crisp 2k, but the difference beetwen what i uploaded and what i was getting from YT was just too big,  Youtube kept showing me this AVC1 encoded crap as "HD":

  

Then you showed me that the clip comes up for you in the better vp09 quality. So i checked with another browser and found the culprit: I had enabled a plugin called "h264ify" on my chrome, once back in time on a really low-spec machine, but it synced to all my computers with chrome... So i disabled h264ify and voilá:

The difference is night and day, even more so in motion.

Thanks for taking a look :-)

[Bridgeboy]

On 6/7/2020 at 2:32 PM, ZenRyder said:

After reviewing this and trying out many different resolutions and bit rates, this is what I recommend based on YouTube specs and what works in the real world.

Resolution: 2k = 2560x1440

Frame rate: 30 fps

Bit rate: 17 mbps - 20 mbps

This gets you the smallest sizes files, but still more resolution and detail than most people need. This will get you the vp09 format.

 

I just received the new Insta360 ONE X2 camera. Can it output 2k video from 360° 5.7K @ 30FPS raw recording? I thought it could only make 1080P video in free capture mode.

Also, you recommend H264? And not Prores?

I'm such a newbie to this stuff.

[btl]

I used h.264 because i know it works  When you export, you can give any resolution as a target. The 1080p from the free capture reframer wil be scaled to whatever you choose.

ProRes422 is relatively new in InstaStudio as an export option. But i 'll try it with the current video i'm editing. Its an Apple format, and i wasn't sure if my non-Macs can even handle it. 

[RagingGrandpa]

Also...

I encode h265 at 1440p, to force vp09 encoding on youtube... (4:3 in this example)

But it always raises my black level by an annoying amount

Anyone found a better way?

Thx

[ZenRyder]

On 11/25/2020 at 12:01 PM, btl said:

I used h.264 because i know it works  When you export, you can give any resolution as a target. The 1080p from the free capture reframer wil be scaled to whatever you choose.

ProRes422 is relatively new in InstaStudio as an export option. But i 'll try it with the current video i'm editing. Its an Apple format, and i wasn't sure if my non-Macs can even handle it. 

I detest all things Apple for more reasons than I care to list. I avoid their codecs and software like the plague. With that said, you can export from Insta360 Studio in 2560x1440 just fine. Then edit in the video editor of your choice and you have a video that YouTube will bless with vp09 codec every time.

[Bridgeboy]

@ZenRyder I have a new Insta360 One X2 that takes great video and the app on the phone is great because it makes it so easy to reframe the video, especially using Viewfinder mode. But when it exports a video from the phone it doesn't let me choose resolution and it ends up a MP4 video in 1080P.

Thing is, it looks great playing from my local PC onto a 4K OLED HDTV, but when uploaded to YouTube it looks like Shiite, I guess because it gets a bad codec. I tried loading the reframed video into Studio 2020 to see if I could re-export it at 2560x1440 but it doesn't allow the 1920 and 1080 be adjusted.

Studio 2020 doesn't have anywhere near the features as the phone App, and is incredible cumbersome to edit and reframe a video by comparison to the app.

I really wish they put all the same features the phone app has into Studio 2020. I don't know what to do, I thought buying this X2 would grant me the ability to make high resolution YouTube videos, but the results are no better than the original Insta360 One .

Edited December 23, 2020 by Bridgeboy

[ZenRyder]

On 12/22/2020 at 8:22 PM, Bridgeboy said:

@ZenRyder I have a new Insta360 One X2 that takes great video and the app on the phone is great because it makes it so easy to reframe the video, especially using Viewfinder mode. But when it exports a video from the phone it doesn't let me choose resolution and it ends up a MP4 video in 1080P.

Thing is, it looks great playing from my local PC onto a 4K OLED HDTV, but when uploaded to YouTube it looks like Shiite, I guess because it gets a bad codec. I tried loading the reframed video into Studio 2020 to see if I could re-export it at 2560x1440 but it doesn't allow the 1920 and 1080 be adjusted.

Studio 2020 doesn't have anywhere near the features as the phone App, and is incredible cumbersome to edit and reframe a video by comparison to the app.

I really wish they put all the same features the phone app has into Studio 2020. I don't know what to do, I thought buying this X2 would grant me the ability to make high resolution YouTube videos, but the results are no better than the original Insta360 One .

Yeah, it kills me when they put new features in a mobile app and then leave out critical ones. This is just one reason why I don't like using phone apps for high powered video editing. Try editing 30 minutes of footage with a phone, yuk! The mobile app is a toy for TikTok clips. You have me wondering what is so incredibly "cumbersome" to reframe on the desktop with the Studio application. Frankly, it works fine for me. It is a little tricky until you understand it, but reframing is quick and easy IMHO.

[Bridgeboy]

1 hour ago, ZenRyder said:

Yeah, it kills me when they put new features in a mobile app and then leave out critical ones. This is just one reason why I don't like using phone apps for high powered video editing. Try editing 30 minutes of footage with a phone, yuk! The mobile app is a toy for TikTok clips. You have me wondering what is so incredibly "cumbersome" to reframe on the desktop with the Studio application. Frankly, it works fine for me. It is a little tricky until you understand it, but reframing is quick and easy IMHO.

Well, the phone app comes with all kinds of Shot Lab features that I haven't even tried yet, however; one of the main features I find intuitive and easy to use for reframing 360 video is the "Viewfinder" option. You simply play your 360 video and hold your thumb on a button on the phone screen to record what is currently displaying on the screen. The button is on a slider so you can slide right or left in real time as the video is playing to zoom in or out; and to reframe to look somewhere else within the 360 video you simply physically turn in space with the phone and look in the desired direction. This is easy when standing up or sitting in a wheeled or swivel chair where you can just spin and look whichever way you want.

I'm sure you can figure out how to do it well on Studio 2020 with practice, but anybody can reframe a video on the phone app to however they want it to look with little to no practice: you simply move the phone in physical space until what you want to view appears on the screen.

That said, I managed to export two 30-minute clips reframing them in this way on the phone (which it exported at 1080P). Then I couldn't get them directly off the phone so I had to upload them to iCloud and redownload them to my PC. I then downloaded the free Open Shot editor and stitched them together and was able to re-export that project to 3840 × 2160 @ 30FPS and uploaded it to YouTube. I know you say you don't have to go that high of resolution to get the VP09 codec, and most watchers won't be watching on 4K anyway; but I have three 4K TVs in my house and if anyone does want to watch it at 4K I wanted to have the full 4K version available on YouTube. It's currently processing the HD version on YouTube and probably still will be for a day or two more.

All of that in that last paragraph is way more then should be necessary to get a good video off this camera; but until I learn how to use Studio better it's the only way I figured out I could still use the phone app editing features...in this case, particularly "Viewfinder" reframing. the 1080P video exported from the phone appear to have enough bitrate (about 30Kbps) that they kept good detail upscaling to 4K.

I'm crash-course learning all this video stuff, and I don't have much spare time to learn anything too cumbersome. In time I'll learn more as I go along, no doubt.

You'll get a chance to see the final product on YouTube once I publish it and you can see what you think. It's hard for me to imagine  Studio 2020 having the ability to reframe video so effortlessly as moving you phone around and aiming it in different directions physically through space. To get that kind of results in Studio I imagine having to pause a lot and place keyframes all over the place and imagine what the transitions will look like or play them back to see how it turned out. On the phone, what you see on the phone screen is what you get...in real time. Or maybe I just don't understand Studio well enough yet.

EDIT: Actually, what timing! The HD version was done processing after I posted this. I just published it:

 

Edited December 28, 2020 by Bridgeboy

[HelpYourVideos]

On 9/28/2020 at 2:13 PM, WILSON-YT said:

I edit all my content through Davinci Resolve Studio - Paid. I try to work with all 4K content now from go pro hero 8 , insta360 (processed through the studio as 3840x2160 h265, full bit rate render) ,mavic air 2 drone. Project setting at start is edited in 3840 × 2160, including timeline , full data levels. I produce the video  3840 × 2160 as a .mp4 file, h264 with a bitrate 30000, network optimized and i leave the rest default. I also render the video with my 1070 and not from my cpu.

Most 10 minute video renders process through my 1070 take about 4 minutes

Youtube takes about 1 hour to upload the 10 minute video file, 30 minutes to make the video show in 1080p and 2 hours for 4K. It is best i can do with my internet speed and not sacrifice too much quality from the original footage.

Hey, I assume you're looking for advice on improving video quality. In no particular order here's some things you can change to improve your workflow and quality.

Two-pass encoding with a defined bitrate will typically result in a worse outcome than picking a low CRF value (say 18-12, usually 16) with a slow (slower, or very slow) preset. What this does is allows the bitrate to fluctuate to accommodate the variation by allocating data when and where it is needed; which means some portions may use ~2kbps and others ~60kbps, for example. 

Another thing that will improve quality is rendering with your cpu using the libx264 or libx265 codecs. GPU's are very fast, however quality will be visibly worse at a given bitrate. Also with GPUs there is less flexibility in the output settings.

You might benefit from enabling "proxy mode" editing instead of using 4k in the timeline. This setting which renders out a low resolution version of your video for you to apply edits to, saving a lot of computer resources. You can make all your edits, then upon export it applies those edits onto your original video.

In addition, I would recommend if you are not color grading the video on a professional monitor, you don't need to use full data levels. What this does is shows and renders in the YUV 4:4:4 color space. Almost all consumer devices use YUV 4:2:0 chroma subsampling and will not benefit from this setting, also youtube will downsample anyway if you upload in 4:4:4. 

Let me know if this makes sense, or is helpful.

[HelpYourVideos]

On 11/25/2020 at 1:48 PM, RagingGrandpa said:

Also...

I encode h265 at 1440p, to force vp09 encoding on youtube... (4:3 in this example)

But it always raises my black level by an annoying amount

Anyone found a better way?

Thx

There is no way to avoid the black level being distorted. Youtube converts rec709 flagged video from 0(black)-255(white) to 16-235 as is the limit for 8-bit shown in the diagram linked below. If you want to test this you can add a chrome extension called colorzilla to use an eyedropper tool on your video and see that the black is at 16.

https://imgur.com/a/fb5z7GN

 

[HelpYourVideos]

On 12/28/2020 at 5:39 PM, Bridgeboy said:

That said, I managed to export two 30-minute clips reframing them in this way on the phone (which it exported at 1080P). Then I couldn't get them directly off the phone so I had to upload them to iCloud and redownload them to my PC. I then downloaded the free Open Shot editor and stitched them together and was able to re-export that project to 3840 × 2160 @ 30FPS and uploaded it to YouTube. I know you say you don't have to go that high of resolution to get the VP09 codec, and most watchers won't be watching on 4K anyway; but I have three 4K TVs in my house and if anyone does want to watch it at 4K I wanted to have the full 4K version available on YouTube. It's currently processing the HD version on YouTube and probably still will be for a day or two more.

All of that in that last paragraph is way more then should be necessary to get a good video off this camera; but until I learn how to use Studio better it's the only way I figured out I could still use the phone app editing features...in this case, particularly "Viewfinder" reframing. the 1080P video exported from the phone appear to have enough bitrate (about 30Kbps) that they kept good detail upscaling to 4K.

One thing most of you guys have not mentioned, which is probably the most important factor regarding video quality is called "generation loss". Each time you export (encode) a video with a "lossy" codec you are changing data and losing quality, almost no matter the bitrate. For this reason its important to take your source video apply all the edits in and encode only one time. 

That said, if you exported those two 30 minute clips with the same parameters, you should be able to losslessly join them also called "concatenate" using a software other than openshot. This avoids encoding a second, or third time and losing more quality. The easiest way to append is probably to open in Avidemux (free) and open one file then go file-> append the second clip and make sure you save in copy mode. If it gives you an error than the clips are not using the same parameters and you have to encode again. Another option is using ffmpeg in command line with the concat command after you list the absolute path to the two files in order in a text document and reference that in your command. Googling these terms will give exact instructions.

[btl]

Thanks for helping me understand that 2-pass is only good to minimize file size. Too bad that Insta Studio has no editing function and one has to export the reframed video in h26x and then take this as the source file for a different editor. I tried VSDC and Premiere Elements since the full Adobe Premiere is simply more expensive than what i would invest in video editing. The Version of Openshot on my Linux box was not very stable and crashed every now and then. Is there a video editor that you would suggest to try if Adobe Premiere is not affordable?

[Meserias]

I'm using ShotCut on my nix box for light editing...
very stable in (my case) in Win as well

[HelpYourVideos]

17 hours ago, btl said:

Insta Studio has no editing function and one has to export the reframed video in h26x and then take this as the source file for a different editor.
Is there a video editor that you would suggest?

If you can, export from insta studio with an absurdly high bitrate, say h264 slow crf 12 or 40-80Mbps. Then delete the file once you’re done editing. 
I would second Meserias, shotcut is free, uses ffmpeg backend which allows for high quality, numerous output options. Shotcut uses a MLT file to store and translate the edits you made in the application to command line instructions for ffmpeg to apply. Which means as you apply edits, it saves instantly and takes very little storage. There is a very active developer and forum. I think they recently added proxy editing. And if I’m reading correctly, they added 360 to equirectangular mask as well? Is this the function that instastudio serves? I’ve never used it.

Edited January 5, 2021 by HelpYourVideos

[Bridgeboy]

@HelpYourVideos Thanks for the tips. Most of it is above my head though.

However, my newest toy is a Skydio 2 that takes great looking native 4K @ 60 FPS. I don't need to deal with framing angles (I forget the term for that already) out of 360° footage.

However, it's pure video with no audio. What I would greatly appreciate advice on is a user-friendly way to add audio (speaking into a microphone while watching the video in real time) and/or adding music (royalty free) to the videos. All while maintaining the quality of the original video. Special effects, titles, etc. would be great to learn eventually as well.

Any ideas?

[HelpYourVideos]

On 2/8/2021 at 10:27 PM, Bridgeboy said:

What I would greatly appreciate advice on is a user-friendly way to add audio (speaking into a microphone while watching the video in real time) and/or adding music (royalty free) to the videos. All while maintaining the quality of the original video. Special effects, titles, etc. would be great to learn eventually as well.

The term you're looking for is "Voice Over". Most Non-Linear Editor (NLE) video software such as shotcut, premiere pro, final cut pro, davinci resolve, etc. will allow you to enable a microphone and record sound while the video is playing. https://www.shotcut.org/blog/video-tutorial-voiceover/ Alternatively, its easy enough to voice record in an audio only software like audacity while watching the video through any video player like vlc or mpv. Then you can examine the waveform and trim it to when you start talking and align the audio manually with the video in the NLE. It is recommended you record audio in .WAV format which allows for lossless editing. You can cut and trim to insert music inbetween or add additional audio tracks if you want music during the voiceover. When you're finished aligning, normalizing, and adding audio effects, output audio as .aac 320k or opus 250k for best quality.

The important thing to remember is that you don't want to re-export the video along with the audio unless you make edits to the video. This will degrade quality. Just import the video to help align your audio edits, and when you export only save the audio file. What you should do next is take your original video and the new audio and "mux" them together losslessly. For this you can use mkvtoolnix, mp4box, or ffmpeg command line. In the first two software you just drag the video and audio and export. It should combine and save almost instantly.

Let me know if that helps.

[Bridgeboy]

On 2/20/2021 at 10:32 AM, HelpYourVideos said:

The term you're looking for is "Voice Over". Most Non-Linear Editor (NLE) video software such as shotcut, premiere pro, final cut pro, davinci resolve, etc. will allow you to enable a microphone and record sound while the video is playing. https://www.shotcut.org/blog/video-tutorial-voiceover/ Alternatively, its easy enough to voice record in an audio only software like audacity while watching the video through any video player like vlc or mpv. Then you can examine the waveform and trim it to when you start talking and align the audio manually with the video in the NLE. It is recommended you record audio in .WAV format which allows for lossless editing. You can cut and trim to insert music inbetween or add additional audio tracks if you want music during the voiceover. When you're finished aligning, normalizing, and adding audio effects, output audio as .aac 320k or opus 250k for best quality.

The important thing to remember is that you don't want to re-export the video along with the audio unless you make edits to the video. This will degrade quality. Just import the video to help align your audio edits, and when you export only save the audio file. What you should do next is take your original video and the new audio and "mux" them together losslessly. For this you can use mkvtoolnix, mp4box, or ffmpeg command line. In the first two software you just drag the video and audio and export. It should combine and save almost instantly.

Let me know if that helps.

It seems like using Shotcut would be easiest, but am I not supposed to export again? How does the audio get embedded with the Video? In that tutorial I don't see him ever export. But in other videos I see people exporting to save the video and audio together.

I guess in that tutorial video you linked, the guy missed the part about just "saving" the project and I assume it would save with the new voiceover embedded in it?

Edited February 27, 2021 by Bridgeboy

[HelpYourVideos]

8 hours ago, Bridgeboy said:

but am I not supposed to export again? How does the audio get embedded with the Video?

Once you have a completed audio track (voiceover+Music+edits), export only the audio (aac is compatible with mp4 and mkv, ogg only mkv) This video might help.

Then you will download either mkvtoolnix or mp4box or use ffmpeg command line (all free/open source) to “mux” the original video file with the audio you just saved. In mkvtoolnix it’s as easy as dragging the video in, then the audio and click start multiplexing to save, it will be done instantly.

[Bridgeboy]

10 hours ago, HelpYourVideos said:

Once you have a completed audio track (voiceover+Music+edits), export only the audio (aac is compatible with mp4 and mkv, ogg only mkv) This video might help.

Then you will download either mkvtoolnix or mp4box or use ffmpeg command line (all free/open source) to “mux” the original video file with the audio you just saved. In mkvtoolnix it’s as easy as dragging the video in, then the audio and click start multiplexing to save, it will be done instantly.

@HelpYourVideos thanks! I did google searching and how-to video watching all day yesterday and figured out most of it but I'm still having problems.

On one 17-minute video,  I matched up 17-minutes worth of music and exported the music by checking the option on the export Codec tab for "Disable Video." I assumed that is how I export only audio and it seemed to work. (I will watch the video above after I post this).

Then I tried to multiplex them together in mkvtoolnix and it kept getting an error and I could not figure it out. The video was MP4 and the audio file was M4A (even though it was set to export AAC). I gathered that mkvtoolnix only is good for MKV files so I thought the error was because I was using an MP4 file.

Then I read boatloads of guides on using FFMPEG and I could not get it to work even though I followed instruction meticulously. I kept getting errors, such as, "'ffmpeg' is not recognized as an internal or external command," among others....so I gave up on that and tried mp4box.

mp4box appeared to work, and it only took a matter of seconds to produce a 13-GB "-muxed" file...I don't understand how a 13-GB file can be created so quickly, and maybe that's what went wrong, I don't know. I started playing the file and it seem perfect! For the first 5:39 of the video that is. At 5:39 mark the video freezes for the rest of the 17-minute video while the music files keeps playing normally for 17-minutes. I had already started uploading to YouTube at this point so I left it uploading to see what would happen. While the standard definition version was processing on YouTube overnight, this morning it showed an error that the video could not process and my only option is to delete it. So, something is definitely wrong with it.

Back to the drawing board again today. I have dozens of cool 4K videos taken with my Skydio 2 with no audio and I can't do anything with them because figuring this out is so difficult!

I got one 4K video uploaded, this one below; but I did export the video with the audio for this one, so it probably lost some detail in the extra iteration of rendering. The only reason I exported it was to get it to work and also due to the extra black screen added at the end of the video, which I guess counts as a edit to the video:

 

[Bridgeboy]

I just made another 17-minute muxed video (a different one) with mp4box and the same exact thing happened: at the 5:43 mark the video freezes for the rest of the 17-minutes...frozen on one frame for the rest of the video while the music plays normally...this is so frustrating!   

Now I tried exporting WAV audio per the tutorial linked above from @HelpYourVideos and then muxing it in mp4box and it goes through 100% of "importing ISO" process, and then goes straight to "Ready..."  and never exports and does not create a muxed file. I have no idea what is going on...

Edited February 28, 2021 by Bridgeboy

[Bridgeboy]

I finally figured it out with ffmpeg!!!!!!!! I had to download and install it! I thought it was just a basic windows command that was preinstalled. This is all I did with AAC audio file output from Shotcut (not WAV):

ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a copy muxed.mp4

This worked within seconds flawlessly. I'm uploading new videos to YouTube now. It will probably take several days to complete all the HD processing on YouTube before they are ready to post.

ffmpeg is definitely the winner! (Once you figure out how to use it). mkvtoolnix and mp4box both had errors each and every time.

 

Edited March 1, 2021 by Bridgeboy

[HelpYourVideos]

7 hours ago, Bridgeboy said:

This is all I did with AAC audio file output from Shotcut (not WAV):

ffmpeg -i video.mp4 -i audio.mp3 -c:v copy -c:a copy muxed.mp4

mkvtoolnix and mp4box both had errors each and every time.

Okay, add ffmpeg to your %Path% so you can call on the program from any directory. 
After the ffmpeg -i you can just drag the file(s) onto command prompt/terminal so there’s no errors in typing the location of the files. Ffmpeg is very powerful indeed, for encoding also not just muxing. But make sure your output is correct because mkvtoolnix should not be giving errors.. did you drag the video in, then drag audio, leaving the default selection of “add as new source file to the current multiple settings” finally click “start multiplex”? 
Here is a link that details what codecs of video and audio are compatible with different containers (such as mp4 and mkv). The common codecs are H264 aka AVC, H265 aka HEVC, VP9, and AV1. All should be supported by both containers. The main benefit of mkv is that allows embedded chapter markers, subtitles and couple other features while being patent unencumbered (likely not an issue for our use cases, haha).

https://en.m.wikipedia.org/wiki/Comparison_of_video_container_formats

Edited March 1, 2021 by HelpYourVideos