Fun fact: most FPV equipment alternates between even and odd fields for each frame it shows to the user. This is why you don't see the interlacing artifacts when there's motion on the screen. It's also why the "resolution" of analog feeds seem so low. It's also why the image bounces by one scanline if you look closely.
I came across your channel quite recently and I have to say that I really appreciate your explanatory series. I feel like this is exactly the content that was missing in the FPV community for so long because prior to your videos this technical information was hardly accessible and not very structured. Many other TH-camrs therefore base their explanations on feel rather than facts which often leads to confusion and no technical understanding. So that is exactly why I enjoy your professional way of producing these videos. Keep up the great work!
This is the best channel for newer pilots for sure. (Maybe experienced guys too, but im newer so idk) In 4 months ive learned how to tune a scratch built quad with a free education from here and others. I cant even imagine the time involved in learning all that on my own, thanks for condensing this stuff so that a simple pipefitter can go from zero to building and tuning quads , you are really doing a great thing here.
@@ChrisRosser thanks for the reply. I still have so much to learn but im not scared of anything quad related anymore. I have alot to learn about pids and blackbox but there is hours of videos for me, and until then im flying everyday with a good enough tune so no complaints 🚀🚀🚀
Thank you for another absolutely amazing and informative video. After your explanation, analog video signal conversion, transmission and reception technology amazes me even more, especially considering the fact that it has been researched such a long time ago!
Thanks for several "oh wow" moments in your video. I sort of knew how it worked at a high level, but had never dug into the details. Thanks for another great video. I'm looking forward to the DJI video one.
Thank you for another great topic. You filled in some areas I either forgot or was hung over in my undergrad engineering classes. Please keep up your amazing videos.
Sir as always a wealth of concise information. Armed with this information, picking out equipment is much easier and a lot cheaper. No more guessing and trying things if you know what you want this information lets you choose the equipment that suits your needs best the first time. Mr. Rosser, I will become a Patreon in the new year, for both yourself and J Bardwell. Can not thank you enough for all the hard work. Happy Holidays
This makes me wonder about having a digital interface between camera/goggle and vtx/vrx, but still analogue ota. Might cleanup the signal abit by reducing interference from the esc/fc. Analogue vtx with mipi in? Nudge nudge, TBS.
@@ChrisRosser I am looking forward to it. It is interesting that the analog signal is converted from digital then back to digital. I am interested in why the Dji system has latency issues. Thank you.
Great video again Chris. Didn't know I wanted to learn about this but hey all knowledge is good eh ! Looking forward to the DJI video, although Good as it is I haven't won the lottery yet. Keep it up my man. Analogue for the time being. 😁
Thanks for the informative video! One question, any solution/chipset (Camera -> VTX -> Receiver) out there that can allow 120fps or higher frame rate? Are there actually other industries improving this technology other than FPV community?
Great question, the analogue video standard is incredibly prescriptive. You can have 525 lines at 60 fields per second or 625 lines at 50 fields per second. That is it. The cost to do anything else is prohibitive because you need to redesign the whole encoder and decoder from scratch and "ain't nobody got time for that" because this tech was developed in the 1940s and 1950s and no-one is working on it anymore! The only reason you have two options is that USA and EU decided to do things differently. DJI delivers 120fps using digital technology.
@@ChrisRosser There are some HD analog protocols that are in active use for security cameras - essentially using NTSC or PAL color with separate luma and chroma. (NTSC and PAL both overlay the chroma on the luma signal for compatibility with pre-color B&W TVs, and actually I stumbled on this video wondering what the analog FPV stuff was using, and... oh, it's just NTSC/PAL. Looks like you all are using something like System D/K for PAL on 5 GHz, and... I'm guessing effectively System M with System D/K bandwidth and audio carrier spacing for NTSC based on what I'm finding?) The big problem, though, with the HD analog security camera protocols is they end up using like ~10x the bandwidth of a standard PAL signal, though. (Some of that will be, they're on a dedicated cable and *can* use that bandwidth - after all, I've used old computers that output ~14 MHz signals with NTSC timing on composite cables to get high-res monochrome - but some of it is actually necessary.) Which, looks like you all use pretty wide channel spacing, but you need tight control of spurious emissions and you'd get fewer channels. (Which is also why Japan's HD analog broadcast system in the 1990s involved quite a lot of advanced compression techniques to cram it into a reasonable bandwidth, and lost a lot of quality during motion, exactly when you'd want maximum quality in an FPV camera.)
Very informative and educational video - thanks! When analogue FPV cameras are advertised as 800TVL or 1200TVL what does this really mean? Is it the initial (digital) image resolution supplied to the image processing chip and is more TVL necessarily better? I'm trying to understand the factors determining the final image resolution you see in your goggles.
Yes the 800 or 1200TVL is the resolution of the digital sensor in the camera. That is the resolution that is then downsampled to standard analgoue resolution. No matter the number of TVL in the camera the resolution of the video is always 525 lines for NTSC and 625 lines for PAL.
Another great video, Chris. I was wondering what the differences were between analog and digital, so it's great that you're starting this series. I have a PID question, unrelated to this video, that I hope you can answer: First, do higher kv motors have better PID handling/ are they easier to tune? My thinking is more power means the quad can respond to PID errors quicker. Second, if the previous is true, could (for example) having 1950kv motors with a throttle limit that mimics the feel of a 1750kv motor mean that a pilot could have the throttle feel that they would prefer while also having superior PID control? The reason I ask is I currently run a 2550kv motor with a motor output limit of 70%. But if I could raise that to 75% and have a throttle limit of 5%, I wonder if the quad would indeed fly better. I tested this myself, but frankly, I don't feel a difference. Perhaps there is a difference, but at my skill level, I can't tell. I don't have blackbox logging, so maybe you could see whether there truly is a difference or not. Looking forward to your response. Whether I'm right or wrong, it will be fascinating to hear what you have to say
Handling is mostly down to motor mechanical torque at low RPM which is to do with motor stator volume. So bigger motors handle better and KV doesn't really matter (in fact too much KV is bad news for handling). I have a video on choosing motors that goes into more detail.
Great content! More information laid out in clear form in one place. Very nice :-) (Joke) Question: "How does analogue video work in FPV?" Answer: "Badly"
The analogue info on the CMOS sensor is just the charge on every R,G and B element in the display (all ~3 million of them!) . The analogue signal from the ISP has had a lot of image processing done has been converted to a single analogue voltage on the wire formatted in a certain way.
this proofs im full blown stupid xD how amazing it would have been having these kind of knowledge taught at school ... about applying mathi this way... so amazing.. one day i will make money out of the hobby and support your patreon.. keep on doing this!! :D
This is a cool video series! Also interesting to point out, that analog video is just digital video transmitted via an analog signal. Didn't know that the actual transmission is frequency modulated only, but I now understand why we got this black and white image in times. That's actually a nice built in failsafe! Could that CCD and global shutter thing actually be a reason, steele likes his ccd so much? I want to do an A+B test now :P
Umm, I think Steele just prefers certain gear because he's used to it not because of any significant performance benefit vs any other setup. CCD sensors are arguably worse than CMOS sensors for FPV because of the lack of WDR and other fancy features.
Unfortunately not. There were some very old protocols used with higher resolution but they were discontinued decades ago and components are no longer in production. In the future we may struggle to source components for analogue video systems now that CCTV is going digital...
Just curious, why isn’t there an HD analog used in FPV then? If the latency of analog is say 15ms and NTSC/PAL is ~500p then you can send a ~1080p analog video in about double the time which would be comparable to DJI latency and a 720p video in barely any more time.
You could transmit twice the resolution but then you would only get half the frame rate (30 fields per second) 15 frames per second. Because you can only send a certain number of lines per second.
I doubt analogue video in ntsc/pal in our goggles is only 30/25 fps. When I'm flying the frame rate looks silky smooth to me, and when watching back the dvr in goggles or on my computer, it is no longer so smooth, it becomes very choppy. On my pc the pal files have a frame rate of 25fps. So I assume in goggles while flying we are seeing a higher frame rate, 60/50 fps I assume. thanks for the video :)
The goggle screen will update 50/60 times per second but only half the lines will actually change! This actually looks smoother (to my eye at least) than a full frame update only 25/30 times a second.
@@ChrisRosser That is not true. The interlaced signal is deinterlaced to 50 or 59.94 progressive frames and all the frames are displayed. So all the lines of the image change every 1/50 or 1/59.94s. This is exactly the same process when you properly process 59.94i DVR recording to 59.94p distribution format. Example: th-cam.com/video/Na9MdQliljU/w-d-xo.html
you are right. You see fully deinterlaced 50p or 59.94p video in your goggles. The downside of most DVRs are that they deinterlace to 25p or 29.97p, so they throw out the half of the information.
PAL might be part of your problem.. Most computer monitors don't run at an multiple of 25fps, which will result in choppy playback. 30fps NTSC DVR will likely look much better on your PC - albeit still not as silky smooth as 60 fields or frames per sec!
@@ChrisRosser Most of the panel control boards incorporate advanced deinterlace mechanisms similar to yadif, bwdif, tomsmocomp, etc. Even the most stupid bob deinterlace is way better that what you describe which is weaving resulting with lost of artifacts that we simply don't see on most goggles.
Because its not that much easier to do SD than HD for digital video! And there would be little benefit to the consumer to justify the development cost.
how to make video 10 times shorter and in one episode: analog signal which is transferred through the air is a very complex signal, it has sinusoids which carry information about colours and brightness and impulses which carry information about frame and lines. Digital signal is just impulses with high frequency. Impulses are easy to synchronise on Rx and TX, but sinusoids are not available to synchronise. So when you have some obstacles the analog signal from tx reflects from them and Rx receives a great mess of sinusoids with high amplitude of main signal and a little bit lower amplitude signals from reflections which are out of phase with main signal (reflected signal is mainly inverted signal and that causes interference of sinusoid or a previous frame which came to the Rx at the same time with current frame but because it's had to move longer distance because of reflections than the main signal). So digital is better))
Fun fact: most FPV equipment alternates between even and odd fields for each frame it shows to the user. This is why you don't see the interlacing artifacts when there's motion on the screen. It's also why the "resolution" of analog feeds seem so low. It's also why the image bounces by one scanline if you look closely.
Hdz gogs dont do this though right? Some deinterlacing magic
I came across your channel quite recently and I have to say that I really appreciate your explanatory series. I feel like this is exactly the content that was missing in the FPV community for so long because prior to your videos this technical information was hardly accessible and not very structured. Many other TH-camrs therefore base their explanations on feel rather than facts which often leads to confusion and no technical understanding. So that is exactly why I enjoy your professional way of producing these videos. Keep up the great work!
Thanks Jakob happy to have you on board!
Very clear explanation. Your video covered all the questions I had. Thank you.
I'm really looking forward to your DJI video. I've been curious on the actual differences between digital and analog video.
I know, I was actually really surprised when I dug into it vs Sharkbyte.
@@ChrisRosser Are you going to go into the differences between the DJI variable latency and Sharkbyte's fix latency?
@@DavePencilguin Yes, I will explain exactly why that's the case!
This is the best channel for newer pilots for sure. (Maybe experienced guys too, but im newer so idk)
In 4 months ive learned how to tune a scratch built quad with a free education from here and others. I cant even imagine the time involved in learning all that on my own, thanks for condensing this stuff so that a simple pipefitter can go from zero to building and tuning quads , you are really doing a great thing here.
If you managed that in 4 months you are doing great and clearly have all the right stuff for this hobby! It took me much longer. Onwards and upwards 😁
@@ChrisRosser thanks for the reply. I still have so much to learn but im not scared of anything quad related anymore. I have alot to learn about pids and blackbox but there is hours of videos for me, and until then im flying everyday with a good enough tune so no complaints 🚀🚀🚀
I love your videos, you are engineering explained for FPV
Wow, thanks! I appreciate your support and encouragement.
Thank you for another absolutely amazing and informative video. After your explanation, analog video signal conversion, transmission and reception technology amazes me even more, especially considering the fact that it has been researched such a long time ago!
Glad it was helpful! It's quite amazing what electronics engineers were able to achieve with no digital electronics at all.
Thanks for several "oh wow" moments in your video. I sort of knew how it worked at a high level, but had never dug into the details. Thanks for another great video. I'm looking forward to the DJI video one.
Oh yeah the DJI video is a step up and the HDZero one even more so!
Thank you for another great topic. You filled in some areas I either forgot or was hung over in my undergrad engineering classes. Please keep up your amazing videos.
Chris thanks for your work. You are a big guy in fpv community. Good luck.
I appreciate that! Glad that my videos are useful to the community 😁
Where have you been the last ten years
Cheers for the great videos
Glad you liked it. Stay tuned for DJI and Sharkbyte up next 😁
And here comes the next top video. Thank you for all the knowledge that you share with us.
Thanks! DJI and Sharkbyte up next 😁😁😁
Sir as always a wealth of concise information. Armed with this information, picking out equipment is much easier and a lot cheaper. No more guessing and trying things if you know what you want this information lets you choose the equipment that suits your needs best the first time. Mr. Rosser, I will become a Patreon in the new year, for both yourself and J Bardwell. Can not thank you enough for all the hard work. Happy Holidays
Thank you for sharing your knowledge with the community. Also AOS 3.5” just came in the mail and can’t wait to try it!
Hope you enjoy it!
Another top notch video from the new FPV guru!
Thanks again!
This makes me wonder about having a digital interface between camera/goggle and vtx/vrx, but still analogue ota. Might cleanup the signal abit by reducing interference from the esc/fc. Analogue vtx with mipi in? Nudge nudge, TBS.
Interesting idea!
Neat. This is very helpful and informative. I love this channel. One of the few that share some uncommon knowledge.
Great video! One of the best I have watched for how these things work.
Thank You Chris Rosser! Awesome Presentation.
My pleasure! I hope you enjoy the DJI and Sharkbyte info just as much. 👍
@@ChrisRosser I am looking forward to it. It is interesting that the analog signal is converted from digital then back to digital. I am interested in why the Dji system has latency issues. Thank you.
Excellent video now I know a litter more of analog video than before so cool .thank U.
Great video! Actually made video transmission understandable to me.
Glad it helped!
Amazing, thanks for making this! I'm looking forward to the other videos
Great series idea. Thanks, Chris 🤝
Glad you liked it!
Great video again Chris. Didn't know I wanted to learn about this but hey all knowledge is good eh ! Looking forward to the DJI video, although Good as it is I haven't won the lottery yet. Keep it up my man. Analogue for the time being. 😁
Thanks, perhaps HDZero will be the system for you? 👍
Thanks Chris.
Any time!
Sweet, more educational material
If you like this you'll love the DJI video up next!
Really appreciate this!
Thanks so much! If you like this the DJI and sharkbyte videos will be even better 😁
Great explanation! Thanks for making this.
Thanks for the informative video! One question, any solution/chipset (Camera -> VTX -> Receiver) out there that can allow 120fps or higher frame rate? Are there actually other industries improving this technology other than FPV community?
Great question, the analogue video standard is incredibly prescriptive. You can have 525 lines at 60 fields per second or 625 lines at 50 fields per second. That is it. The cost to do anything else is prohibitive because you need to redesign the whole encoder and decoder from scratch and "ain't nobody got time for that" because this tech was developed in the 1940s and 1950s and no-one is working on it anymore! The only reason you have two options is that USA and EU decided to do things differently. DJI delivers 120fps using digital technology.
@@ChrisRosser There are some HD analog protocols that are in active use for security cameras - essentially using NTSC or PAL color with separate luma and chroma. (NTSC and PAL both overlay the chroma on the luma signal for compatibility with pre-color B&W TVs, and actually I stumbled on this video wondering what the analog FPV stuff was using, and... oh, it's just NTSC/PAL. Looks like you all are using something like System D/K for PAL on 5 GHz, and... I'm guessing effectively System M with System D/K bandwidth and audio carrier spacing for NTSC based on what I'm finding?)
The big problem, though, with the HD analog security camera protocols is they end up using like ~10x the bandwidth of a standard PAL signal, though. (Some of that will be, they're on a dedicated cable and *can* use that bandwidth - after all, I've used old computers that output ~14 MHz signals with NTSC timing on composite cables to get high-res monochrome - but some of it is actually necessary.) Which, looks like you all use pretty wide channel spacing, but you need tight control of spurious emissions and you'd get fewer channels. (Which is also why Japan's HD analog broadcast system in the 1990s involved quite a lot of advanced compression techniques to cram it into a reasonable bandwidth, and lost a lot of quality during motion, exactly when you'd want maximum quality in an FPV camera.)
Very informative and educational video - thanks! When analogue FPV cameras are advertised as 800TVL or 1200TVL what does this really mean? Is it the initial (digital) image resolution supplied to the image processing chip and is more TVL necessarily better? I'm trying to understand the factors determining the final image resolution you see in your goggles.
Yes the 800 or 1200TVL is the resolution of the digital sensor in the camera. That is the resolution that is then downsampled to standard analgoue resolution. No matter the number of TVL in the camera the resolution of the video is always 525 lines for NTSC and 625 lines for PAL.
We can definitely send 1080i signals over a wire analog. Why did wireless analog transmission stop at 480p?
@@voxtelnismo Thanks, glad it's not physics limited.
@Chris Rosser
Thx you very much for this exciting video, i am looking fwd for this series.
But should i fly my cams now in pal or ntsc mode?
Depends, PAL gives more detail at lower frame rate. NTSC gives less detail but a higher frame rate. It's up to you...
Great as usual!keep it up!
Another great video, Chris. I was wondering what the differences were between analog and digital, so it's great that you're starting this series. I have a PID question, unrelated to this video, that I hope you can answer:
First, do higher kv motors have better PID handling/ are they easier to tune? My thinking is more power means the quad can respond to PID errors quicker. Second, if the previous is true, could (for example) having 1950kv motors with a throttle limit that mimics the feel of a 1750kv motor mean that a pilot could have the throttle feel that they would prefer while also having superior PID control?
The reason I ask is I currently run a 2550kv motor with a motor output limit of 70%. But if I could raise that to 75% and have a throttle limit of 5%, I wonder if the quad would indeed fly better. I tested this myself, but frankly, I don't feel a difference. Perhaps there is a difference, but at my skill level, I can't tell. I don't have blackbox logging, so maybe you could see whether there truly is a difference or not.
Looking forward to your response. Whether I'm right or wrong, it will be fascinating to hear what you have to say
Handling is mostly down to motor mechanical torque at low RPM which is to do with motor stator volume. So bigger motors handle better and KV doesn't really matter (in fact too much KV is bad news for handling). I have a video on choosing motors that goes into more detail.
Great content! More information laid out in clear form in one place. Very nice :-)
(Joke)
Question: "How does analogue video work in FPV?"
Answer: "Badly"
Digital is the future no doubt.
Nice video man.
Is there anywhere that I can contact you regarding an issue I'm having with my latest analog setup?
What is the difference between the analogue information that the ADC receives and the analogue video signal sent from ISP?
The analogue info on the CMOS sensor is just the charge on every R,G and B element in the display (all ~3 million of them!) . The analogue signal from the ISP has had a lot of image processing done has been converted to a single analogue voltage on the wire formatted in a certain way.
I suggest show how to make a scrambler and descrambler for analog video
this proofs im full blown stupid xD how amazing it would have been having these kind of knowledge taught at school ... about applying mathi this way... so amazing.. one day i will make money out of the hobby and support your patreon.. keep on doing this!! :D
Glad I could help!
So why it's not possible to increase resolution of analog signal? I mean why it can't look like digital?
There is in fact an analog HD (security camera) standard, but bandwidth is kind of a problem.. Those run at 30fps afaik
off topic but maybe you could make a video explaining how the IMU works in betaflight?
Good suggestion I'll add it to the list
This is a cool video series! Also interesting to point out, that analog video is just digital video transmitted via an analog signal. Didn't know that the actual transmission is frequency modulated only, but I now understand why we got this black and white image in times. That's actually a nice built in failsafe! Could that CCD and global shutter thing actually be a reason, steele likes his ccd so much? I want to do an A+B test now :P
Umm, I think Steele just prefers certain gear because he's used to it not because of any significant performance benefit vs any other setup. CCD sensors are arguably worse than CMOS sensors for FPV because of the lack of WDR and other fancy features.
@@ChrisRosser Ok, fair enough :)
can you suggest open source softwares to convert the analog signal into video? or what i need to learn to do so?
wouldn't the post de-interlacing be 30fps for NTSC and 25fps for PAL?
Absolutely right yes. 30 frames (60 fields) per second for NTSC. 25 frames (50 fields) per second for PAL.
I've been wondering. Are there any other protocols besides NTSC and PAL that would work well for us?
Unfortunately not. There were some very old protocols used with higher resolution but they were discontinued decades ago and components are no longer in production. In the future we may struggle to source components for analogue video systems now that CCTV is going digital...
The Ethix CCD Camera uses a CCD Global shutter
Good to know thank you, there are still some out there!
so awesome
Appreciate it. I think you'lll love the DJI and Sharkbyte versions 👍
I know it is out of price for most of us but clearview have a hd system. Is it possible for you to reach them and add there system to this serie???
Just curious, why isn’t there an HD analog used in FPV then? If the latency of analog is say 15ms and NTSC/PAL is ~500p then you can send a ~1080p analog video in about double the time which would be comparable to DJI latency and a 720p video in barely any more time.
You could transmit twice the resolution but then you would only get half the frame rate (30 fields per second) 15 frames per second. Because you can only send a certain number of lines per second.
when will the ISP come with AI upscale as well
Actually, 59.94 for NTSC if you really want to get down to it and 60 for PAL60!
I doubt analogue video in ntsc/pal in our goggles is only 30/25 fps. When I'm flying the frame rate looks silky smooth to me, and when watching back the dvr in goggles or on my computer, it is no longer so smooth, it becomes very choppy.
On my pc the pal files have a frame rate of 25fps. So I assume in goggles while flying we are seeing a higher frame rate, 60/50 fps I assume.
thanks for the video :)
The goggle screen will update 50/60 times per second but only half the lines will actually change! This actually looks smoother (to my eye at least) than a full frame update only 25/30 times a second.
@@ChrisRosser That is not true. The interlaced signal is deinterlaced to 50 or 59.94 progressive frames and all the frames are displayed. So all the lines of the image change every 1/50 or 1/59.94s. This is exactly the same process when you properly process 59.94i DVR recording to 59.94p distribution format. Example: th-cam.com/video/Na9MdQliljU/w-d-xo.html
you are right. You see fully deinterlaced 50p or 59.94p video in your goggles. The downside of most DVRs are that they deinterlace to 25p or 29.97p, so they throw out the half of the information.
PAL might be part of your problem.. Most computer monitors don't run at an multiple of 25fps, which will result in choppy playback.
30fps NTSC DVR will likely look much better on your PC - albeit still not as silky smooth as 60 fields or frames per sec!
@@ChrisRosser Most of the panel control boards incorporate advanced deinterlace mechanisms similar to yadif, bwdif, tomsmocomp, etc. Even the most stupid bob deinterlace is way better that what you describe which is weaving resulting with lost of artifacts that we simply don't see on most goggles.
I don't understand why we cant have small, lightweight and economical digital standard definition
Because its not that much easier to do SD than HD for digital video! And there would be little benefit to the consumer to justify the development cost.
That was awesome! Thanks!!
Glad you liked it!
how to make video 10 times shorter and in one episode: analog signal which is transferred through the air is a very complex signal, it has sinusoids which carry information about colours and brightness and impulses which carry information about frame and lines. Digital signal is just impulses with high frequency. Impulses are easy to synchronise on Rx and TX, but sinusoids are not available to synchronise. So when you have some obstacles the analog signal from tx reflects from them and Rx receives a great mess of sinusoids with high amplitude of main signal and a little bit lower amplitude signals from reflections which are out of phase with main signal (reflected signal is mainly inverted signal and that causes interference of sinusoid or a previous frame which came to the Rx at the same time with current frame but because it's had to move longer distance because of reflections than the main signal). So digital is better))
There is quite a bit more going on! But I'm sure Chris will cover that soon ;)
@@lievenvv also if real latency of analog fpv goggles is less than 50ms it seems to me that real resolution of the picture you see is 720x288...
how to make an analog video scrambler and descrambler?