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- Acharya T.

Acharya T. - John Wiley & Sons, 2000. - 292 p.
ISBN 0-471-48422-9
Download (direct link): standardforImagecompressioncon2000.pdf
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JPEG2000 Part 1 codec without any interframe coding. The MJ2 format is designed to contain not just one or more JPEG2000 image sequences but also other information such as audio annotations and streaming requirements. The overall presentation of Motion JPEG2000 is called a movie. As shown in Figure 10.6, a movie is a collection of tracks. Each track is a timed sequence of media data, called samples. Samples are numbered in sequence based on timed unit. There are many different kind of tracks, but the three most important tracks are video track, audio track, and hint track. They are used for two different purposes. The video and audio tracks are used to contain media data. The purpose of a hint track is to carry instructions for packing one or more tracks for a streaming protocol.
Similar to the JP2 file format discussed in Section 8.3, the fundamental building block of the MJ2 file format is called a box. All the data are contained in structure boxes, and no data are outside the box structure. Basi-
PART 3: MOTION JPEG2000 263
File
Movie Box
Movie Header Box
Track Box
Track Header Box
Media Box
Media Header Box
Header Reference Box
Media Information Box Media Information Header Box
Data Information Box Data Reference Box
Sample Table Box Time to Sample Box
Sample Description Box
Fig. 10.7 File structure (boxes) of a Motion JPEG2000 movie with one track.
cally, Part 3 of the JPEG2000 standard is nothing but definitions of boxes and guidelines for how to use them. There are 30 boxes defined in this file format. Figure 10.7 shows an example of the box structure for a MJ2 file with one track. Part 3 also provides guidelines for how to use the JPEG2000 codec with frequency weighting in order to improve the subjective quality of reconstructed image sequence. Motion JPEG2000 has a very wide range of
264
BEYOND PART 1 OF JPEG2000 STANDARD
applications such as digital still cameras with video capture capability, remote surveillance, etc., where a high-quality frame-based, approach is desired.
10.4 PART 4: CONFORMANCE TESTING
JPEG2000 Part 4 [4] defines the conformance testing for JPEG2000 Part
1 [1]. The standard specifies three procedures: decoder compliance testing procedure, encoder compliance testing procedure, and JP2 file format reader compliance testing procedure. The whole testing procedures are based on two profiles and three compliance classes (Cclass). The two profiles (profile 0 and profile 1) defined in “JPEG2000 Part 1, Amendment 1 Code Stream Restrictions”, are used for compliance testing. Testing an arbitrary codestream (which requires unlimited resources) is out of the scope of conformance testing. A profile provides limitations on compression parameters such as tile size, LL subband resolution, subsampling factor, marker locations, and others. So a decoder can define its capabilities for the bitstream within a profile. The three compliance classes (Cclass 0, Cclass 1, and Cclass 2) define different levels of image-quality guarantees for a decoder. The compliance level for an implementation under test (IUT) should be reported based on profile x Cclass y. The decoder and encoder compliance test procedures are as follows.
• Decoder compliance test procedure: The decoder compliance test procedure can be summarized as follows: First, decode all the test codestreams using the decoder under test (the test code-streams are supplied by the standard). Second, compare decoded images with the reference image; if all the errors are within the defined tolerance (based on the error metrics provided in the standard), then the decoder under test is reported as profile x Cclass y compliant.
• Encoder compliance test procedure: The encoder compliance test procedure can be summarized as follows: First, encode all the selected test images with different compression parameters using the encoder under test. Second, if the reference decoder can fully decode all the encoded code-stream, then the encoder under test passes the compliance test.
A compliant JP2 file format reader must be able to decode the code-stream within the JP2 file. In addition, if the decoded components are not all at the same resolution, the reader should be able to upsample them into the same resolution and convert to full resolution sRGB [17] color space from the source color space. A set of test JP2 files and reference images are provided in the Part 4 standard. The test procedure just simply decodes the test file and compares with the corresponding reference images. If the differences of all the test files are within the defined tolerances, the JP2 file format reader is compliant with the standard.
OTHER PARTS (7-12) 265
The Part 4 compliance test files include bare code-stream, JP2 files, reference decoded images, and description files for the test data. The reference decoder is defined in JPEG2000 Part 5: Reference Software [5], which we will review in the next section. However, it should be noted, it is explicitly stated in Part 4 of the JPEG2000 standard document that compliance testing does not include acceptance testing, performance testing, or robustness testing.
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