I'm just writing this entry as a little reminder for myself, but if you find it useful too then that's superb!
By default YouTube plays their low quality version of all videos and external applications also fetch this low quality version by default.
I'll actually use a real video from my music video collection for this.
To view "Esprit Sur Un Voyage" in any web browser, embedded player, or fetch application the URL is as follows:
To view a higher quality version of this same video, &fmt=18 has to be appended to the end of the video URL. I've noticed that while the video image quality still suffers notably at this setting the audio goes from low quality mono to good quality stereo. sample as follows:
And finally to view to video in 720p HD, the original quality of the video, &fmt=22 has to be appended to the end of the URL as follows:
If there is only a High Quality version of a video but no HD version fmt=18 will work but fmt=22 will do nothing and the video will run at low quality. Likewise if there is no high quality version of a video at all the fmt= setting does nothing at all.
There! Now it's in a nice easy to access place so I won't forget about it!
These tag additions don't appear to work in embeds, but they do work for fetch applications.