user16354: Is that possible, that a video (.mp4 or etc) had two video streams and we could to do work with each stream individually ? (like we do with 2 audio streams and we can remove any of them)..
if so:
1)  do you know which video editors can handle such videos? Adobe Premiere , Sony Vegas, DaVinci or ... ?
2) At this moment, my typical MP4 files are converted by youtube (after upload) to i.e. mpeg-4 10 AVC. And will those 2-stream videos will be converted to 1-stream video anyway? (maybe I have to ask that to YT forum, right?)

user22271: This is certainly possible, and rather easy to do, for example with MKVToolnix, adding the second file as new source to current settings (just darg & drop the files)


Matroska video can handle multiple streams, and so can mp4. MKVToolnix gives only mkv as output I think. For various output formats a good  tool is dmMediaConverter, which is less known but is a great ffmpeg frontend.


The output has the expected size of the two input sizes added up.
As for playing the resulting movie and switching between the video streams, VLC can do it, as well as Gnome Mpv (in Linux). SMPlayer was less good (sometimes jumped forward when switching or just crashed). MPV with pseudo-gui has no option for the switch. (Tested in Linux.)

user6273: Yes. MPEG-4 Part 14 (the MP4 container format) supports any number of objects (e.g. video, audio and subtitle streams) and isn't limited to only one stream per content type.
In practice however, you seldom see a video file that has multiple video streams, because the range of applications for this is very limited. I would also advise you not to put multiple video streams into one file, as (a) users don't expect it, many won't know how to switch the video track or not notice there is a second video track at all and (b) many players (soft- and hardware) aren't equipped to play files with multiple video streams and either won't have any option to switch between streams or fail to play the file completely.
It is also more common to use Matroska (.mkv) containers for video files with multiple audio/subtitle streams, but even with those, you rarely see files with more than one video stream.

16354: <p>Is that possible, that a video (.mp4 or etc) had two video streams and we could to do work with each stream individually ? (like we do with 2 audio streams and we can remove any of them)..</p>

<p>if so:</p>

<p>1)  do you know which video editors can handle such videos? Adobe Premiere , Sony Vegas, DaVinci or ... ?</p>

<p>2) At this moment, my typical MP4 files are converted by youtube (after upload) to i.e. <code>mpeg-4 10 AVC</code>. And will those 2-stream videos will be converted to 1-stream video anyway? (maybe I have to ask that to YT forum, right?)</p>
 22271: <p>This is certainly possible, and rather easy to do, for example with <a href="https://mkvtoolnix.download/" rel="nofollow noreferrer">MKVToolnix</a>, adding the second file as new source to current settings (just darg &amp; drop the files)</p>
<p><a href="https://i.stack.imgur.com/fyr2u.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fyr2u.png" alt="enter image description here" /></a></p>
<p><a href="https://i.stack.imgur.com/0Gu6G.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0Gu6G.png" alt="enter image description here" /></a></p>
<p>Matroska video can handle multiple streams, and so can mp4. MKVToolnix gives only mkv as output I think. For various output formats a good  tool is <a href="http://dmsimpleapps.blogspot.com/2014/04/dmmediaconverter.html" rel="nofollow noreferrer">dmMediaConverter</a>, which is less known but is a great ffmpeg frontend.</p>
<p><a href="https://i.stack.imgur.com/AKpOg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AKpOg.png" alt="enter image description here" /></a></p>
<hr />
<p>The output has the expected size of the two input sizes added up.</p>
<p>As for playing the resulting movie and switching between the video streams, VLC can do it, as well as Gnome Mpv (in Linux). SMPlayer was less good (sometimes jumped forward when switching or just crashed). MPV with pseudo-gui has no option for the switch. (Tested in Linux.)</p>
 6273: <p>Yes. MPEG-4 Part 14 (the MP4 container format) supports any number of objects (e.g. video, audio and subtitle streams) and isn't limited to only one stream per content type.</p>

<p>In practice however, you seldom see a video file that has multiple video streams, because the range of applications for this is very limited. I would also advise you not to put multiple video streams into one file, as (a) users don't expect it, many won't know how to switch the video track or not notice there is a second video track at all and (b) many players (soft- and hardware) aren't equipped to play files with multiple video streams and either won't have any option to switch between streams or fail to play the file completely.</p>

<p>It is also more common to use Matroska (.mkv) containers for video files with multiple audio/subtitle streams, but even with those, you rarely see files with more than one video stream.</p>
