Peter McLennan wrote:Need help with video data rate.
VLC reports "content data rate" from an h.265 file in default configuration the from BMD app is
"57770 kb/sec", That's kilobits per second, right?
To get megabits per second from kilobits per second, I need to divide that number by a thousand.
That works out to 57.77 mbps. That doesn't seem right. What's up?
What lens? What ISO (high noon sun or good light, low light or night)? Frame rate? Video size (I assume 3840x2160) etc.
Noise influences bitrate (the more noise, the higher the bitrate, unless Apple's noise reduction becomes brutal).
First: It's not really that good. It's about the best, that "unadulterated" default Apple App h265 delivers. Blackmagic Camera does NOT improve on that in any way.
Cinema P3 Pro handles up to typical 25 Megabyte/second (~200 megabit/sec - 20MB setting) and around 45Megabyte/second (~350 megabit/sec - 40MB setting). Compare this to ProRES 422HQ (around 750 megabit/sec), ProRES 422 (around 475 megabit/second) ProRES 422LT (around 350 megabit/sec).
Just to name the "alternative App", that allows really impressive h265 performance. Just because it's a Blackmagic product, does not mean, it is capable of delivering better results in most cases (just, maybe more fine tuned results in some case, but far from all).
Often h265 is ridiculed for "real work"; it should lead to stuttering and whatnot during editing. True enough for weak-chested notebooks, but in todays world, that may be the least of your troubles.
On my MacBook 14 Pro M1 Pro h265 is handled without any hiccups at any speed even "skirting" manually through material at vastly increased framerates. Older computers (especially non Apple-silicon) without hardware supported decoding may show "strain" doing that, but otherwise h265 shouldn't pose any real problems on even modest modern silicon.
The 20MB and 40MB settings in Cinema P3 Pro are ideal for saving space, compared to using ProRES 422LT or better. Only problem is, that the h265 material only has 4:2:0 chroma handling instead of a slightly more accurate 4:2:2 format in ProRES.
I have a high quality h265 codec in my Ninja V, that delivers up to around 250 megabit/sec (25 fps, UHD, 10-bit 4:2:2 XQ quality) and 300 megabit/second for 50 fps, when fed from my Lumix S5. That's completely indistinguishable from any ProRES 422 (even HQ) from the same camera in real life editing (even when pixel peeping). The 30+ to near 40 Megabyte/second certainly is dramatically lower, than around 90+ Megabyte/sec from the same connection, when recording ProRES 422 HQ in the same format (25fps).
The popular description of the two format types: ProRES formats are designed to ease the editing phase to the smoothest possible use (requires lots of space), whereas h265 is designed to cram maximum possible quality into minimum space resp. LAN/WiFi/Radio etc transmission bandwidth (especially important in broadcast systems, where bandwith may be highly restricted).
IF you need to guarantee maximum recording quality, ProRES 422HQ opens up to conserve more fine details, than even h265 4:2:0 40MB using Cinema P3 Pro on an iPhone 15 Pro.
For professional use, it's a no-brainer. If you can't afford the storage as a professional, you're in the wrong business.
Compared to 12-bit 5,9k 25 fps ProRES RAW, demands are in the "tiny" region (my recordings reach around 2.2+ Gigabit/second in ProRES RAW HQ, and around 1.5+ Gigabit/second in simple, near "pedestrian" ProRES RAW

Each RAW frame is around 19.5 megapixel in size or VERY detailed, compared to standard UHD. If maximum quality, best possible malleability and flexibility in post is required, that's the way to go. It's the video version of the difference between still imaqes in RAW, versus the more limited HEIF/HEIC or worse jpeg formats.
Hobbyists may decide, that the 20MB h265 setting for the same recording conditions, may be the best compromise between quality and storage requirements on "travel walkabout" or similar "run and gun" situations, that mostly are subject to only "cut and render" with a minimum of grading and whatnot.
If you "only" have around 150GB of free storage (or less) on your iPhone 15 Pro at the beginning of a day collecting travel memories, the choice between being limited to let's say 27-28 minutes (25 fps, UHD, ProRES 422HQ) or being able to "splatter" video to your hearts content for up to around 100 minutes in h265 20MB setting in exactly the same circumstances, and relegate culling to a more relaxed backup session at the hotel later in the evening (still leaving 30GB for around 300 odd RAW 48 megapixel images, if your real available storage is 180GB on your iPhone)
Regards