Camera I/F's

In article <0ae*nenww@news.chiark.greenend.org.uk>, 
theom+news@chiark.greenend.org.uk says...
> 
> Don Y <blockedofcourse@foo.invalid> wrote:
> > In some cases, I might want high frame rates at the expense of detail.
> > In other cases, the exact opposite.  Most of the frames may get discarded
> > to concentrate on "areas of interest" -- based on an analysis of the
> > *entire* frame (at a slower rate).
> > 
> > I use cameras to access a variety of "field conditions" that are otherwise
> > hard to instrument.  Tweaking the software or optics (or even the choice
> > of image sensor) is easier than having to move to a different processor
> > (family) to meet a different application.
> 
> One thing worth pointing out is that talking to a camera in CSI or other
> native format gives you essentially unprocessed RAW data.  On a smartphone
> the ISP processor does (quite a lot of) image processing to turn the
> pixels into an acceptable JPEG image.  This includes all of the vendor
> tricks like dual cameras, HDR, white balance, etc.
> 
> If you just want JPEGs you can slap down a network connection, you might
> want a chip that does all the image processing for you, which is what you
> get in USB/etc land.  If you want to attach to a raw sensor then be prepared
> to budget for some compute (and software) to tidy up the images for you.
> 
> Theo

People like Connexant, Averlogic and others do chips for converting 
stills or streams into JPEG, H.264, MPEG 2 or 4..

Makes the processing requirements in the camera a LOT less

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Paul <paul@pcserviceselectronics.co.uk> wrote:
> People like Connexant, Averlogic and others do chips for converting 
> stills or streams into JPEG, H.264, MPEG 2 or 4..
> 
> Makes the processing requirements in the camera a LOT less

It depends what you want the images for.  For example, here's the cropped
RAW output of a Raspberry Pi CSI camera against the processed output:
https://www.pic-upload.de/view-30656067/2016-05-15-RAW-vs-Processed.jpg.html

To produce the image on the right you have to do various noise filtering and
colour compensation.  If this is video you have to do it on every frame. 
Less than JPEG, but not insignificant.

Theo

Hi Theo,

On 7/10/2017 2:09 AM, Theo Markettos wrote:
> Don Y <blockedofcourse@foo.invalid> wrote:
>> In some cases, I might want high frame rates at the expense of detail.
>> In other cases, the exact opposite.  Most of the frames may get discarded
>> to concentrate on "areas of interest" -- based on an analysis of the
>> *entire* frame (at a slower rate).
>>
>> I use cameras to access a variety of "field conditions" that are otherwise
>> hard to instrument.  Tweaking the software or optics (or even the choice
>> of image sensor) is easier than having to move to a different processor
>> (family) to meet a different application.
> 
> One thing worth pointing out is that talking to a camera in CSI or other
> native format gives you essentially unprocessed RAW data.  On a smartphone
> the ISP processor does (quite a lot of) image processing to turn the
> pixels into an acceptable JPEG image.  This includes all of the vendor
> tricks like dual cameras, HDR, white balance, etc.

Yes.  But, if you are doing anything beyond just shipping that video
to a remote location, then you typically *want* access to the raw
video.  And, often don't care about color purity, etc.

E.g., if you are looking for signs of *motion* in an image, you want to
be able to apply a mask to the raw image and then look for changes in
the selected portions of the image.  If the image has been compressed,
this is harder to do in the general case.

Likewise, doing facial feature extraction/recognition, you don't really care
if the flesh-tones are way off hue (e.g., greenish) as you're really looking
for shapes, sizes and relative placements of those "features".  Again,
harder to do with a JPEG than with the raw pixels from which it was
distilled.

In each of these cases, you might conditionally (or unconditionally) *ALSO*
prepare a compressed data stream (to reduce transport/storage costs) to ship
off to be recorded or post-processed elsewhere.

> If you just want JPEGs you can slap down a network connection, you might
> want a chip that does all the image processing for you, which is what you
> get in USB/etc land.  If you want to attach to a raw sensor then be prepared
> to budget for some compute (and software) to tidy up the images for you.
> 
> Theo
>