Burn aspect ratio overlays into h264 video

[glitterball]

I realise that this suggestion may sound ludicrous, but bear with me...

If there was a way to permanently record black overlays at the top and bottom of the image in camera (since the aspect ratios cannot be modified), then the video files would be substantially smaller and therefore allow for an increase in quality and FPS.

I don't know if there would be a bottleneck at the compression stage, but I'm thinking that this could allow either the Bit rate/FPS to be jacked up and so, overcome the SD card buffer bottleneck on the 600d.

A simple test here showed that h264 files are 25% smaller with 2.4:1 black overlay embedded. If many users are throwing those extra pixels away in post anyway, then it could give a nice quality boost to those of us who can't record 1920x1080 in raw.

[glitterball]

I'm surprised that I got no replies...

Can anyone answer if this would be feasible to do? Could overlays be inserted before the compression is done?
Also,  would the potential bit rate increase significantly improve the video quality?

I know from trial and error that the subject matter has a huge part to play in how high I can set the CBR rate on my camera, but I'm not sure about just how much of an increase in image quality the increased CBR rate will yield.

[ItsMeLenny]

Similar things have been questioned before (such as burning in a time stamp).

It is somewhat technically possible, but I don't think it would easily be implemented OR be very stable if it was.

[ItsMeLenny]

And in addition *

The quality increase will be barely anything if anything, and you could get better quality just by increasing the bit rate instead.

And it won't help in any way whatsoever with increasing frame rate as the frame rate is capped due to hardware limits.

It would probably only help with file size.

The SD bottleneck isn't so much a problem in h264, as it's barely using any of its potential in the first place from what I've seen.
So bit rate can be increased somewhat without problems.

The only advantage I see in burning in black bars was if information in text form were to be recorded into the black area.
Shutter, Aperture, FPS, Picture Style and info.

[glitterball]

Thanks for the reply.

I still think that there is potential in the idea, because the ability to increase the CBR in Magic Lantern seems to be entirely scene-dependent.
For example: I can easily crank the CBR to 3.0x if I leave the lens cap on (entirely dark scene), I can go to 2.0x for some simple indoor scenes, but if I try to record a very detailed and dynamic outdoor scene, then it can struggle at 1.3x.

[ItsMeLenny]

I still think that there is potential in the idea, because the ability to increase the CBR in Magic Lantern seems to be entirely scene-dependent.
For example: I can easily crank the CBR to 3.0x if I leave the lens cap on (entirely dark scene), I can go to 2.0x for some simple indoor scenes, but if I try to record a very detailed and dynamic outdoor scene, then it can struggle at 1.3x.

Yeah, I guess that's not surprising.

A couple of things to take into account is that the h264 stream in lower end cameras is stretched out from a smaller size, this size differs between cameras (basically the max raw recording resolution), which it also doesn't match up to the resolution of the aspect ratio overlays. So technically you wouldn't be burning that overlay image onto the h264. But one could technically calculate the black area of the resolution to aspect. But again, you'd be calculating that buffer, not the 1920x1080 h264.

I can't seem to find the post that was about this before, you may have to do some deeper digging. I recall the post was about burning a timestamp into black bars in h264.


Edit:
Here's one unhelpful post http://www.magiclantern.fm/forum/index.php?topic=2675.msg11068#msg11068