- Posts: 1185
- Joined: Fri Jul 01, 2016 11:07 pm
Its been coming up a lot lately, so I decided to throw together a test that demonstrates the relationship between constant quality encoding and what ultimately ends up on YouTube.
Steps:
To quantify the quality of each file, I used ffmpeg to calculate its SSIM. It's not the best metric available, but it's far from the worst.
The following graph shows the SSIM of the h.265 uploads, and the YouTube h.264 streams compared to the DNxHR master. The graph shows that as you approach lossless, you hit a YouTube re-encoding brick wall, and that uploading higher quality files, is just wasting bandwidth.
The following graph again shows the YouTube brick wall, as the bitrate stays relatively constant regardless of quality of the upload.
Steps:
- Rendered a 1080p clip out of resolve as DNxHR 444 10-bit.
- Trans-coded the clip to h.265 444 10-bit, using various CRF values ranging from 0 (lossless) to 50 (horrendous).
- After uploading all the clips to YouTube and allowing it to process them, I pulled down all of the h.264 420 8-bit files that youtube uses to stream.
To quantify the quality of each file, I used ffmpeg to calculate its SSIM. It's not the best metric available, but it's far from the worst.
The following graph shows the SSIM of the h.265 uploads, and the YouTube h.264 streams compared to the DNxHR master. The graph shows that as you approach lossless, you hit a YouTube re-encoding brick wall, and that uploading higher quality files, is just wasting bandwidth.
- ssim.png (16.62 KiB) Viewed 6520 times
The following graph again shows the YouTube brick wall, as the bitrate stays relatively constant regardless of quality of the upload.
- bitrate.png (14.47 KiB) Viewed 6520 times
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