Last week I discovered that you could send ProRes/audio 16-bit Integer (Big Endian), Stereo (L R), 48.000 kHz videos to Youtube without having to convert the video to h.264/ACC.
I tested sending ProRes 422, LT and HQ. All videos were accepted by YouTube. The example below was ProRes HQ/audio 16-bit Integer (Big Endian), Stereo (L R), 48.000 kHz 2.57 GIG file. I was surprised that YouTube took a video over 2 GIGS, which is their upload file size limit.
One of the things you need to do to the video is to have Fast Start enabled. YouTube has a hard time encoding videos that aren't Fast Start and may not convert the video correctly.
If your using Compressor set the streaming to Fast Start. In FCP 7, 6 or 5 export the video as a self-contain video. This will enable the Fast Start. I can't comment on FCP X because I don't have it.
Motion doesn't enable Fast Start when exporting to ProRes. Here are a few things you can do to enable fast start in Motion.
1) Share, send to Compressor and set Streaming to Fast Start.
2) Share using Compressor settings. You need to make a ProRes Setting in Compressor with Fast Start enable.
3) Download this free app that will enable Fast Start in any Quicktime video file:
Below is a better example of a ProRes video, compared to the video I posted here last week. For better viewing change the video resolution or to 1080p full screen.
File Extension: mov
Estimated size: 2.59 GB
16-bit Integer (Big Endian), Stereo (L R), 48.000 kHz
Width: (100% of source)
Height: (100% of source)
Selected: 1920 x 1080
Pixel aspect ratio: Square
Frame rate: (100% of source)
Frame Controls: Automatically selected: Off
Codec Type: Apple ProRes 422 (HQ)
Multi-pass: Off, frame reorder: Off
Automatic gamma correction
Pixel depth: 24
Spatial quality: 75
Min. Spatial quality: 0
Temporal quality: 0
Min. temporal quality: 0
In my opinion ProRes is a better choice when you want to keep your video quality when sending to YouTube compared to sending a h.264 video. An added plus is you don't have to convert your video to h.264.