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I was wondering, the bitrate is fixed at 100Mbps, is it safe to assume that 24p gives more detail than 30p? It should leave 20% more room for detail for every frame...
Image quality 24 vs 30p (h265)?
- Thread starter FlyingUser
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I'm not sure I understand what you're looking for as far as detail. Detail on the video or the FPV?
24P is the frame rate. 24P will lend itself to a more cinematic effect. It looks better and more natural. If you're looking for a sharper image, 30P will be better. Less motion blur.
I'm assuming he means - if 100mbps is the Phantom's data rate for video, then will shooting lower frame rates result in each frame containing more data, due to less frames being compressed into 100mbps.
It's something I've never really thought about, but I dare say yes, you're probably right.
It's something I've never really thought about, but I dare say yes, you're probably right.
Subjectively no....
The apparent increase in sharpness from the higher frame rate will more than exceed any detail loss that might exist.... you can’t make a call here on basic mathematics. Any impact from the compression schemes isn’t linear and very subject dependent.
The apparent increase in sharpness from the higher frame rate will more than exceed any detail loss that might exist.... you can’t make a call here on basic mathematics. Any impact from the compression schemes isn’t linear and very subject dependent.
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Yes, this is what I meant. Never seen it discussed, only 30p vs 60p in h.264.
Thanks! I often shoot very slow stuff, flying high or moving slow around the target, I thought about these situations.
It's a bad assumption the 100mbps write bit rate never stops. Writing at 100mbps will start and stop depending on what's in the buffer memory, available to write to SD. If it's empty, it stops and waits. As the frame rate or resolution increases the frequency of stopping will be less. Hence, you won't see any quality difference between 24 and 30FPS as far as resolution or clarity in each frame.
The P4P, although it supports 100mbps, cannot keep up with 4096X2160 @ 60FPS, even though DJI says it does. It's barely too much to handle. You'll see glitches in the video every once in a while. Reducing resolution to 3840X2160 @ 60FPS it does just fine, no glitches. Notice M2P doesn't support 4K at 60FPS at all, even though it supports the same 100mbps write speed, and the H3 Ambarella chip used in the M2P claims to support 4K@60FPS. You might say the M2P is writing at half throttle.
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i read this at 1/4 throttle and I'm still unsure what your saying...
Are you suggesting the 100Mbs spec is useless as the AC cant write to the SD card at that speed reliably?
Btw- can you please share where you learnt the M2 is carrying a H3? I haven't seen that confirmed anywhere yet.
Thanks,
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Thanks for the input, but I meant the possible between the h.265, 3840×2160 24p and 30p modes here (spec says 100Mbps for both). Didn' bother with 4096x2160 yet, since I don't have a screen with that aspect ratio and my goal here is to maximize image data for each frame anyway.
Also thought about using the burst mode and create a 6k video, but the p4p is not very fast when it comes to burst stills...
A decent SD-card itself is certainly not a bottleneck here, 100Mbps translates to 12.5MB/sec write speed, which is not a challenge for most modern cards. Any glitches should come from the camera's circuitry.
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I totally believe it's writing at 100mbps, no question. What I'm saying is it's not always writing, it will start and stop, depending on what's in the codec's buffer memory to write to SD. With slower FPS and lower resolutions the data collected will not keep the chip running full speed all the the time. With slower FPS it will run full speed until the buffer is empty, stop and wait for more data, then start writing at full 100mbps speed till the buffer's empty then stop, and so on. It's not happening exactly as I describe since there is a slight ramp time to each segment write, but in general this is how it should work with most flash controllers for these processors. So my point is for slower FPS like 24 or 30, the chip is not working hard, running half throttle, easy to keep up, and no difference in quality should be noticed between 24 and 30FPS, regardless if it's h.264 or 265.
These are digital systems. The data collected from the sensor is captured and compressed in hardware the same way all the time. More time to compress has no benefit, but too little time will drop frames, like occurs occasionally when capturing with 4096X2160@60FPS on P4P (M.264). The capture either works, or it doesn't, there's no in-between with compressing with hardware routines for M.264 or 265. The M.265 is a better codec that compresses better, providing smaller files, but many say it's harder to compress and decompress. This is evident because P4P can't support 4K@60FPS using M.265, which implies the processor can't keep up with so much data collection. So although m.265 makes smaller files, more efficient, and should reproduce better images (versus m.264) after decompressed to view, it takes more CPU performance because it's a lot more work, to compress for storage, and decompress to view.
As for 4096X2160@60FPS (M.264) with P4P, I believe this mode is on the ragged edge of the P4P's ability to keep up, and 100mbps isn't quite fast enough, running full speed all the time. The evidence is that occasionally the P4P camera will fall behind and drop frames to the SD card, hence an occasional glitch appears from the buffer being overrun, or overfilled so to speak. It needs to drop frames to catch up. These frame drops happen 5 to 10 times during a 20min flight, but they don't happen at all when recording 3840X2160@60FPS (m.264), which I deem within the chips ability to keep up, regardless of the video scene.
As for the H3 being in M2P, there was a photo of an M2P taken apart showing the H3. I believe I saw that in MavicPilots.com forum, likely in the M2P section. If I run across it I'll insert a link to it.
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Ok. I'm gonna go stick a fork in my eye because I'm too stupid to understand what ya'll are telling me!
This isn't the place I first saw the H3 mentioned, I still haven't found that photo of the M2 disassembled, however this guy mentions the M2 using the H3.
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I've never understood why 24FPS (Cinematic Effect) is preferred by so many as opposed to 30FPS. Is it simply nostalgia? Would Hitchcock have used 30FPS if it were available? Is it because they had no other choice but to use 24FPS in order to properly expose the film?? I inadvertently used 24FPS on a shoot last year and still regret it. Just didn't like it... choppy....
Hitchcock might have used 30fps if he was in the USA. The 24/30fps thing is dependent on region and whether PAL or NTSC is the standard. It all comes back to line frequency where earlier television sets obtained the sync frequency for the picture tube scanning directly from the line frequency (50 or 60hz).
Ditto. Maybe 12 fps or less is even more cinematic then?! I have always disliked the "cinematic" jerky panning when going to the cinema. Maybe that's why I think Hobbit at 48 fps isn't so bad everyone seems to suggest! (I live in a PAL country so 24 fps vs 25 fps should be negligible). ;-)
Some info on why 24fps. Having said all this, I shoot 30fps to avoid jerky pans. And I think the look is close enough to cinematic vs. 60 FPS.
That speed is just above the low end of what our brain is able to perceive as fluid video, but with just enough imperceptible stutter that it creates a pleasing, cinematic look. Film is shot at 24FPS. It's really all an illusion in our brain.
And that's where the polarizers come in. Gotta keep the exposure from blowing up!
Beware of H.265 on the P4P. Unless it’s been fixed in later firmware (haven’t heard that it has) I believe there is a bug which had me pulling my hair out till I finally tried reverting to H.264 and never had the problem again.
When shooting continuous video over, I think, the 5 or so minute mark, a new video file is started. This is normal as it reaches max filesize at that point. But most times when the new file is started it will drop about a dozen frames a second or so into the new file. This does not happen when using the H.264 setting.
When shooting continuous video over, I think, the 5 or so minute mark, a new video file is started. This is normal as it reaches max filesize at that point. But most times when the new file is started it will drop about a dozen frames a second or so into the new file. This does not happen when using the H.264 setting.
P3P 4K video is 60 Mb/s and the file system splits files at 4 GB i.e. at about each 9 minutes.
I often forget to start a brand new video clip just before starting a longish Litchi mission. I then have to try to hide the few dropped frames at the 9 minute break point. I haven't found a perfect solution but I have added 2+2 frames to both sides of the clip breakpoint with Final Cut so the split point does not seem so jerky.
I often forget to start a brand new video clip just before starting a longish Litchi mission. I then have to try to hide the few dropped frames at the 9 minute break point. I haven't found a perfect solution but I have added 2+2 frames to both sides of the clip breakpoint with Final Cut so the split point does not seem so jerky.
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