What is the difference between -raw and -dng in CHDK PTP???

blenderbach

39

« on: 02 / June / 2023, 17:39:58 »

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I took two pictures, one using rs -raw and the other with rs -dng commands in CHDK PTP. The DNG opens up in all softwares with a black border around the image plus the entire image area of the sensor is visible. The RAW, on the other hand, opens as RAW image data in other software, and produces a black and white version of the image with the black border, with a lot of noise. However, RawTherapee can open this RAW normally, but for some reason, the black border is completely gone and it even slightly crops the image, even though, from what I can tell, all cropping and processing is turned off. Any ideas? Thanks!

IMGDNGGRAB.jpg (485.36 kB, 2888x2136 - viewed 4 times.)

IMGRAWGRAB.jpg (849.43 kB, 2832x2120 - viewed 4 times.)

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reyalp

13948

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #1 on: 02 / June / 2023, 19:58:40 »

Quote from: blenderbach on 02 / June / 2023, 17:39:58

I took two pictures, one using rs -raw and the other with rs -dng commands in CHDK PTP. The DNG opens up in all softwares with a black border around the image plus the entire image area of the sensor is visible. The RAW, on the other hand, opens as RAW image data in other software, and produces a black and white version of the image with the black border, with a lot of noise. However, RawTherapee can open this RAW normally, but for some reason, the black border is completely gone and it even slightly crops the image, even though, from what I can tell, all cropping and processing is turned off. Any ideas? Thanks!

With -dng, you get a DNG format image, which includes metadata and should be loadable by any software that correctly implements DNG support. With -raw, you get "CHDK raw" which is just a framebuffer dump, and is only supported by software that implements CHDK raw support for the specific camera. The underlying raw data is effectively the same in either case, but software may render them differently.

With DNG, how much of the sensor area is rendered may vary depending on the CHDK "default crop" setting, and whether the particular software renders the default crop or active area.

edit:
The difference in brightness and apparent noise is just due to the software using different defaults for the conversion from raw to displayable colors for the different formats.

« Last Edit: 02 / June / 2023, 20:01:33 by reyalp »

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blenderbach

39

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #2 on: 02 / June / 2023, 20:51:21 »

Quote from: reyalp on 02 / June / 2023, 19:58:40

With -dng, you get a DNG format image, which includes metadata and should be loadable by any software that correctly implements DNG support. With -raw, you get "CHDK raw" which is just a framebuffer dump, and is only supported by software that implements CHDK raw support for the specific camera. The underlying raw data is effectively the same in either case, but software may render them differently.

Thanks for the information, but I have selected the entire sensor for the DNG, not a crop. When I do DNGs, they come out as a full sensor image, along with the black non-working part of the sensor border. For some weird reason, when I do the plain RAW, it crops the image. I thought it's supposed to be the RAW framebuffer, so technically it shouldn't cropping either. It should be the full sensor image, and yet, it's cropping. Is it an issue with CHDK PTP, or is there a reason for this? Thanks.

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reyalp

13948

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #3 on: 02 / June / 2023, 23:06:08 »

Quote from: blenderbach on 02 / June / 2023, 20:51:21

For some weird reason, when I do the plain RAW, it crops the image. I thought it's supposed to be the RAW framebuffer, so technically it shouldn't cropping either. It should be the full sensor image, and yet, it's cropping. Is it an issue with CHDK PTP, or is there a reason for this? Thanks.

No. It's almost certainly a default crop hard-coded in whatever program you are using view the CHDK raw.

When you use -dng in chdkptp, it gets the raw data in exactly the same way it would with -raw, and then combines it with a DNG header (and swaps the byte order as required for DNG).

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blenderbach

39

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #4 on: Yesterday at 03:03:07 »

Perhaps maybe you know of a software that I could use to edit/view the RAW raws? Because I was using RawTherapee and RawHide. Both softwares had this crop. Those were RAWs from my S3IS. When it came to my SX40HS, they couldn't even open the RAW. I have no clue what to do. Since you've been doing this for many years, you probably have some expertise in this area, and perhaps know of a software that can do this.

The reason I want the RAW raws, is to do some sensor testing. I'm interested to see how many dead pixels I have and also I want to see if I can unlock that black border of dead sensor to perhaps make it work, bringing my 12.1MP to a full 13MP.

Afterwards, I have a certain idea to test. I want to see if I can use CHDK PTP while recording a video, and seeing if CHDK PTP can offload each RAW movie frame as soon as it hits the movie buffer. After all, the frames have to be captured first, meaning they are RAW before they hit the conversion. If I can grab a hold of them, through the CHDK PTP, I can get my laptop to do all the heavy lifting, while the camera just relays the data over USB. Since upon some research, it seems that even if I could make it happen in-camera, the SD Card can't take such high speed RAW offloading, but USB might.

The thing is, it seems that video research for CHDK is being looked over and pretty much ignored. Last talk about video was like 2008-2009. The thing is, video is also a major part of these cameras. CHDK runs on a bunch of cameras, and yet, only works with photos, and the only thing with video is the compression. Seems to me that if I don't do it, no one will.

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reyalp

13948

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #5 on: Yesterday at 21:10:36 »

Quote from: blenderbach on Yesterday at 03:03:07

Perhaps maybe you know of a software that I could use to edit/view the RAW raws? Because I was using RawTherapee and RawHide. Both softwares had this crop. Those were RAWs from my S3IS. When it came to my SX40HS, they couldn't even open the RAW. I have no clue what to do. Since you've been doing this for many years, you probably have some expertise in this area, and perhaps know of a software that can do this.

I'd suggest using DNG. As I described before, the actual image data is the same. The difference is that for CHDK "raw", each program needs special support for every camera. As for software, it depends what you actually want to do with it. For processing raw into pretty pictures, raw therapee is fine.

For analyzing raw data, you probably want something else. If you want to inspect unprocessed raw data from a CHDK DNG, you can use the chdkptp dngdump command to extract it in a more common format, for example

Code: [Select]

dngdump -rfmt=16pgm -raw

gives you a 16 bit, non-debayered greyscale PGM, which you could load into gimp or convert further with common tools.

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The reason I want the RAW raws, is to do some sensor testing. I'm interested to see how many dead pixels I have

If you use DNG, you can use the chdkptp dnglistpixels command to identify pixels with values in a particular range. See https://app.assembla.com/spaces/chdkptp/wiki/DNG_Processing

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and also I want to see if I can unlock that black border of dead sensor to perhaps make it work, bringing my 12.1MP to a full 13MP.

This is extremely unlikely, IMO. At least some of the black borders are physically masked on the sensor, so the are already read out, but contain only noise and dark current.

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Afterwards, I have a certain idea to test. I want to see if I can use CHDK PTP while recording a video, and seeing if CHDK PTP can offload each RAW movie frame as soon as it hits the movie buffer.

IMO, there is no raw data visible to the main CPU during movie recording. Whatever YUV data eventually gets turned into compressed video is generated directly during readout, similar to how live view works, and indeed, in some cases the live view buffer is use directly for video. So at best, you will find uncompressed YUV at the same resolution as the native video file.

It has to be this way, since the system does not have the bandwidth to read out and process full resolution images at video frame rates, and again, we know the live view works this way.

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After all, the frames have to be captured first, meaning they are RAW before they hit the conversion. If I can grab a hold of them, through the CHDK PTP, I can get my laptop to do all the heavy lifting, while the camera just relays the data over USB. Since upon some research, it seems that even if I could make it happen in-camera, the SD Card can't take such high speed RAW offloading, but USB might.

These cameras only support USB 2. In practice, the fastest CHDK supported cams top out around 33 mbyte/s of user data, and older ones are significantly less.

FWIW, what you describe is essentially how the chdkptp live view works.

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blenderbach

39

Re: What is the difference between -raw and -dng in CHDK PTP???

« Reply #6 on: Today at 00:19:45 »

Alright, thanks for the information!

Quote from: reyalp

IMO, there is no raw data visible to the main CPU during movie recording. Whatever YUV data eventually gets turned into compressed video is generated directly during readout, similar to how live view works, and indeed, in some cases the live view buffer is use directly for video. So at best, you will find uncompressed YUV at the same resolution as the native video file.

It has to be this way, since the system does not have the bandwidth to read out and process full resolution images at video frame rates, and again, we know the live view works this way.

So, you're saying it's possible to get raw 640x480 video? Since you mentioned I can find uncompressed YUV at the same resolution.

Also, you talked about bandwidth and read-out limitations, so what if we cheat a bit? Instead of filming at full-resolution, why not film at 720i? The camera is capturing a handful of lines, instead of progressive. Shouldn't that lighten the load and allow for 720 resolution in video?

Although, if I recall correctly, no one has even figured out how the video is created by these cameras, so I don't know... Not to mention Canon Camcorders like the Vixia HF S20 aren't even supported by CHDK, yet they also have a photo mode, that getting a RAW image from would be nice, but yeah... I have no idea...

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