user24100: Our workflow involves huge 8K clips(i.e., 8192x8192). The inputs are mostly very high bitrates 264/265 clips, though we are using ProRes or  DNxHD for post-production within the process, we do not want to archive such huge files as the "master" copies(easily over 100GB for 1 minute).
My current approach is, using FFMPEG to compress the ProRes/DHxHD clips into H.265 clips using a very high-quality setting (crf=12, slow profile).
Another quality related setting is the pixel format config. Then my question comes up:
Targeting the same clips(5 of them), using the same compress settings, one with yuv420 8-bit, one with yuv444 10-bit, yuv444 outputs are constantly smaller than yuv420 outputs(5%-10%), i.e, lower bitrates.
If yuv444 10-bit needs to store more information, how could this be possible?

user1760: From Why does 10-bit save bandwidth (even when content is 8-bit)?

When encoding with the 10-bit tool, the compression process is
  performed with at least 10-bit accuracy compared to only 8-bit
  otherwise. So there is less truncation errors, especially in the
  motion compensation  stage, increasing the efficiency of compression 
  tools. As a consequence, there is less need to quantize to achieve a
  given bit-rate.
The net result is a better quality for the same bit-rate or conversely
  less bit-rate for the same quality: between 5% and 20% on typical
  sources.

See the link for additional info.

24100: <p>Our workflow involves huge 8K clips(i.e., 8192x8192). The inputs are mostly very high bitrates 264/265 clips, though we are using ProRes or  DNxHD for post-production within the process, we do not want to archive such huge files as the "master" copies(easily over 100GB for 1 minute).</p>

<p>My current approach is, using FFMPEG to compress the ProRes/DHxHD clips into H.265 clips using a very high-quality setting (crf=12, slow profile).</p>

<p>Another quality related setting is the pixel format config. Then my question comes up:</p>

<p>Targeting the same clips(5 of them), using the same compress settings, one with yuv420 8-bit, one with yuv444 10-bit, yuv444 outputs are constantly smaller than yuv420 outputs(5%-10%), i.e, lower bitrates.</p>

<p>If yuv444 10-bit needs to store more information, how could this be possible?</p>
 1760: <p>From <a href="http://x264.nl/x264/10bit_02-ateme-why_does_10bit_save_bandwidth.pdf" rel="nofollow noreferrer">Why does 10-bit save bandwidth (even when content is 8-bit)?</a></p>

<blockquote>
  <p>When encoding with the 10-bit tool, the compression process is
  performed with at least 10-bit accuracy compared to only 8-bit
  otherwise. So there is less truncation errors, especially in the
  motion compensation  stage, increasing the efficiency of compression 
  tools. As a consequence, there is less need to quantize to achieve a
  given bit-rate.</p>
  
  <p>The net result is a better quality for the same bit-rate or conversely
  less bit-rate for the same quality: between 5% and 20% on typical
  sources.</p>
</blockquote>

<p>See the link for additional info.</p>
