BUG (v15.4.1) - h264 encodes are poor quality on M1 MacMini
h264 exports done on an M1 MacMini show significantly more compression artefacts than those done on non-M1 hardware. In investigating the problem I noticed that the file sizes are significantly smaller than expected and digging into the export shows that the resultant bitrate is only around 60% of what it should be. This is across all the built-in presets that use single-pass h264 hardware encoding as well as any custom ones. To prove the point I encoded the same file on several platforms, (both Mac and PC), with several export presets. See the attached file that shows the results.
h264 exports on M1 hardware only achieve 60-65% of the target bitrate, where-as other hardware is in the 80-90% range.
Bitrate isn't the whole story as increasing it such that the resultant file has the intended bitrate still produces files with more noticeable macro-blocking, (although the differences are now more subtle).
I have also tried using v22.1 BETA of both Premiere and Media Encoder, which give the same low bitrate exports on M1 hardware.
Mayank Jain commented
Hi AndyC, Sorry for this problem again. We have made some fixes to increase the bit rates(file sizes) of exported files in the latest beta build(188.8.131.52 or higher) and consequently improve the quality of exported files. You should see better bit rates(file sizes) now on M1 machines in all exported files. Please check the latest beta build and let us know how it goes.