Saturday, August 3, 2013

SnappyCam takes 8MP full-res Photos on the iPhone at 20fps (or so it says)


The SnappyCam app is quite popular among iOS users, as it allows us to take snapshots at faster rates than the native camera app. Unfortunately, to do so it had to drop the picture quality to 3MP. But now, in its latest version, its developers says it has made a breakthrough that allows his app to take full resolution 8MP photos at 20fps in an iPhone 5.

To do so, John Papandriopoulos says it had to completely reinvent the way JPEG works, in order to maximize every step of the image processing process, from the sensor data to the buffering and compression and storage of the final images. I have nothing personal against Mr. Papandriopoulos, but when I come across something that seems too good to be true... my feelings are highly doubtful.

I doubt that the iPhone 5 CMOS sensor array is even capable of working at that speed at full resolution, which would be something quite close to the requirements for the sensor to be able to record UltraHD 4K video.

If we consider raw data from the sensor (meaning, just 1 byte of data for each of its 3264x2448 pixels - which will be processed somewhere down the line - debayering to produce a color image) a FullHD video stream would require about 59MB/s throughput, that would be processed and compressed using the hardware encoder/codecs. To process a 8MP image at 20fps, you're talking more that twice that amount: 154MB/s.

If there was a "mysterious" way to make the sensor work at that pixel rate, you would also be able to make it recorde Full HD video at over 60fps.

Looking at the example photos on the official site, anyone can see those are not full resultion 8MP photos. At the very best those are interpolated lowe resolution photos bumped up in size to make it look like they have more resolution (with no extra detail than the lower resolution photos).

If you're willing to trust him, do go ahead and buy the SnappyCam - but if you do, please do a quick test comparing the photos taken with the native camera app, and one captured at 20fps with this app.

2 comments:

  1. You might find this engineering blog post helpful,

    http://www.snappylabs.com/blog/snappycam/2013/08/03/snappycam-imaging-in-depth/

    where it is shown that SnappyCam does not do any upsampling from a low-resolution image to shoot at 8 Mpx on the iPhone 5.

    :-)

    ReplyDelete
    Replies
    1. @jpap thanks for the link, will give it a look.

      Delete

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