Method for using a JPEG engine to assist in efficiently constructing MPEG I-frames
View Patent ↗A camera or other imaging device or other system configures its JPEG engine to produce a JPEG image that is in compliance with the JPEG specification but specially constructed. The configuration is chosen such that the JPEG image information for pixels of an image is stored in 8- or 16-bit groups, unlike a typical JPEG image in which image information is stored in groups of varying numbers of bits. A final software step reads the JPEG image information and constructs an equivalent MPEG I-frame. The 8- and 16-bit grouping in the JPEG image facilitates efficient conversion from JPEG to MPEG.
1. A method for constructing MPEG I-frames comprising the steps of;
a) configuring a JPEG engine to produce JPEG data in which all discrete cosine transform coefficients are encoded in a byte-aligned manner; and
b) performing JPEG processing, using the JPEG engine, on an uncompressed digital image of a scene, producing JPEG data in which the discrete cosine transform coefficients are encoded in a byte-aligned manner; and
c) reading the JPEG data;
d) converting the JPEG data to MPEG data; and
e) constructing an MPEG I-frame comprising the MPEG data.
2. The method of claim 1 farther comprising the step of storing the MPEG data in an MPEG file.
3. The method of claim 2 , further comprising the step of adding file header information to the MPEG file.
4. The method of claim 1 wherein the step of configuring the JPEG engine is accomplished by specifying table generating values that are used by the JPEG engine to generate Huffman code tables.
5. The method of claim 1 , further comprising the steps of:
a) providing conversion tables for converting JPEG data in which discrete cosine transform coefficients are encoded in a byte-aligned manner to MPEG data; and
b) performing the step of converting the JPEG data to MPEG data using the conversion tables.
6. A digital imaging device comprising:
a) a lens for focusing light; and
b) an electronic array light sensor for receiving the focused light from the lens; and
c) a logic unit for controlling the digital imaging device and receiving image information from the electronic array light sensor, the logic unit comprising a microprocessor system and a JPEG engine, the logic unit adapted to
i. configure the JPEG engine to produce a data stream in which discrete cosine transform coefficients are encoded in a byte-aligned manner; and
ii. convert the data stream to an MPEG data stream representing an MPEG I-frame.
7. The digital imaging device of claim 6 wherein the digital imaging device is a camera.
8. An image compression system comprising:
a) means for obtaining an uncompressed digital image; and
b) means for performing JPEG image processing; and
c) means for configuring the JPEG processing means to produce a JPEG-compliant data stream in which all discrete cosine transform coefficients are encoded in a byte-aligned manner; and
d) means for converting the data stream to a data stream representing an MPEG I-frame.