I have the exact issue with my projects for H264 exporting.
This issue was found when I switch to M1 version of Adobe products. it wasn't that noticeable with the Intel version using Rosetta 2.
Hardware encoding for H264 was unacceptable bad with anytime bitrate.
Software encoding was better but still have artifact with double bitrate.
the same video upload to YouTube and download the H264 version is looking better with the smaller file size.
I notice this since the first version of the Apple Silicon Adobe product, and now Feb 16, 2022 and this issue is not yet solve.
Here's some reference:
MacBook Pro (13-inch, M1, 2020) 16GB RAM 1TB storage
OS version: MacOS Monterey 12.2.1
Premiere Pro 22.2.0 Build 128
Media Encoder 22.2 Build 64
Format: QuickTime
Preset: AppleProRes 422
Quality: 100
Width: 1920
Height: 1080
Frame Rate: 50
Field Order: Progressive
Aspect: Square Pixels (1.0)
HDR Graphics White (Nits): 203 (75% HLG, 58% PQ)
Depth 8-bpc
Filesize:
00:29:48:37 / 51.46 GB
Format: H.264
Preset: Match Source - High bitrate
Width: 1920
Height: 1080
Frame Rate: 50
Field Order: Progressive
Aspect: Square Pixels (1.0)
Encoding Setting
Performance: Hardware Encoding
Profile: Main
Level: 4.2
Export Color Space Rec.709
HDR Graphic White (Nits): 203 (75% HLG, 58% PQ)
Bitrate Setting
Bitrate Encoding: VBR, 1 pass
Target Bitrate [Mbps]: 10
Filesize:
00:29:48:37 / 1.64 GB
Format: H.264
Preset: Custom, base on “Match Source - High bitrate” double bitrate and software encoding
Width: 1920
Height: 1080
Frame Rate: 50
Field Order: Progressive
Aspect: Square Pixels (1.0)
TV Standard: PAL
Encoding Setting
Performance: Software Encoding
Profile: Main
Level: 4.2
Export Color Space Rec.709
HDR Graphic White (Nits): 203 (75% HLG, 58% PQ)
Bitrate Setting
Bitrate Encoding: VBR, 1 pass
Target Bitrate [Mbps]: 20
Maximum Bitrate [Mbps]: 24
Filesize:
00:29:48:37 / 4.54 GB
Using ProRes 422 Source upload to YouTube and download from YouTube
Format: H.264
Preset: unknown (YouTube)
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.29.100
Duration: 00:29:48.80, start: 0.000000, bitrate: 2390 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 2252 kb/s, 50 fps, 50 tbr, 90k tbn, 100 tbc (default)
Filesize:
00:29:48:37 / 534.4 MB