Tom's Life Bits

You've loaded an old revision of the document! If you save it, you will create a new version with this data.

===== JPEG Information =====

Digital Cameras save images in JFIF (usually incorrectly called JPEG or if you're an MS-DOS user JPG) format. Anyway, "JPEG" files consist of "markers" which separate out each part of the file. For example, every JPEG starts with a "start of image" marker and stop with an "end of image" marker. Most markers are followed by 2 bytes which tell the number of bytes that fit in the frame that was marked with this marker. After that the data follows. So what markers are in a typeical JPEG? These markers should exist in all JPEG files:
  * Unordered List Item

* 0xffd8 - Start Of Image
  * 0xfffe - Comment (Optional)
  * 0xffdb - Quantization Table
  * 0xffc0 - Start Of Frame (Baseline)
  * 0xffc4 - Huffman Table (Sometimes ommited from mjpeg files)
  * 0xffda - Start Of Scan (This is the actual compressed image)
  * 0xffd9 - End Of Image

Why These Images Are Corrupt

So what's on a JPEG created by this camera:

* 0xffd8 - Start Of Image
  * 0xffe1 - Application Data
  * 0xffdb - Quantization Table
  * 0xffc4 - Huffman Table
  * 0xffc0 - Start Of Frame (Baseline)
  * 0xffda - Start Of Scan
  * 0xffd9 - End Of Image

This is all okay except for in the example file I used there are 8 extra padding bytes before the 0xffd9 and a bunch of extra garbage after the file. Actually, it seems to be padded by 11 bytes, but the IJG library only seems to complain about the 8 byte padding. I haven't seen another JPEG library that pads bytes tho. As far as the data at the end, I wonder what it looks like under a disassembler. I'm just glad I'm not using Windows or Internet Explorer to look at these images.

Anyway, after removing the 8 bytes of padding and the extra crap at the end of each file, the images open without any complaint. An interesting note: At the top of the file in the application data section, there appears to be some camera information here:

SQ Tech. Co., Ltd. SQ908 MEGA-Cam. CSTN FW Build 2.6.2007:01:06

Maybe firmware built after this date doesn't have this issue in it.

Edit summary

Note: By editing this page you agree to license your content under the following license: CC Attribution-Noncommercial-Share Alike 4.0 International