The entire frame is compressed as a whole, without prior decomposition into blocks of pixels
It is worth underlining that the entire frame is compressed as a whole, without prior decomposition into blocks of pixels. Some consider that the artefacts at low bitrates are thereby visually much more acceptable than the well known blocking effects of the DCT based coding schemes, which may sound subjective.
Lastly, the output JPEG 2000 code stream presents an inherently scalable structure along several dimensions: colour components, resolutions (via the DWT), quality (via the rate-distortion optimization) and spatial regions thanks to an appropriate packetisation of the data.
JPEG 2000 as an intermediate master format for the broadcast production workflow
An important demand of the industry today is high quality masters compatible with a wide range of delivery formats that can make the content available on any relevant existing platforms. This includes ingest, trans-coding, captioning, quality control and audio track management as linked processes. JPEG 2000 displays all the necessary features of such a high quality intermediate service master format: • Quality: The high quality is preserved throughout the production process.
• Bit depth: JPEG 2000 is a 10 bits or higher format. • No blocking artefacts. • Scalability: this holds the promise of “create once for multiple purposes”.
• Easy editing: Even at the highest bit rates, its intrinsic flexibility makes it very usable on today’s laptop and workstation editing systems, with a limited number of full bit rate real-time video tracks. As computing hardware improves, the number of real-time layers can only increase.
• Intra-frame coding: Unlike motion compensation based compression methods referring to previous (P) or future (B) frames for inter-frame prediction, the intra-frame JPEG 2000 allows cutting the video signal at any place.
• Easy trans-coding: For high-end applications, trans-coding to an intermediate version may improve the workflow. JPEG 2000’s unobjectionable compression artefacts ensure that this is a clean as well as a quick operation when bit rate is at a premium. Correctly trans-coded 1920x1080 JPEG 2000 files @ 100 Mbit/sec have been found to be subjectively indistinguishable by most viewers from their 2048x1556 2K originals. Furthermore the wavelet based JPEG 2000 compression does not interfere with the final, usually DCT based, broadcast format.
JPEG 2000 as contribution format
Whether the contribution is over a satellite or fibre channel, given the move to HDTV and 3D-HDTV, compression is still required. Here again, the need for compression goes with a demand for high quality, which led most contribution system providers to integrate JPEG 2000.
Figure 2: JPEG 2000 maintains the same level of quality after multiple generations of encoding and decoding.
• Robust transmission, reduced video artefacts: Bit errors in a JPEG 2000 stream produce less visual artefacts than in GOP and DCT-based formats, as the errors appear as a short-lived blur in the impacted picture, without propagation to neighbour frames.
• Symmetrical Encoding/Decoding processing power: In systems with a small number of encoders and a large number of decoders, it is important to lighten the decoders as much as possible at the expense of the complexity and cost of the encoders. This is the philosophy behind MPEG-2 and MPEG-4. The architecture of contribution systems is very different, with the number of transmitters and receivers much more equally matched. The cost and complexity of the transmitter and the receiver should therefore ideally be about the same, with JPEG 2000 this is relatively easily achieved, as the encoding and decoding are symmetric processes.
19
In 2009, the standardization of a flexible carriage of JPEG 2000 streams over MPEG-2-TS was initiated. It will define all necessary identifiers and field descriptors in future amendments of the MPEG-2-TS standard. This work follows the new standard JPEG 2000 broadcast profile to be published soon.
Other key-features in favour of using JPEG 2000 for video transmission are: • Very low latency: Reducing latency is crucial for live TV contribution. In the case of motion compensation, pictures are encoded using reference to past and future pictures with a consequent latency relative to the size of the full group of pictures (GOP). The intra-frame nature of JPEG 2000 compression reduces the latency. On average, JPEG 2000 produces latency of less than 1.5 frames for encoding or decoding. Some implementations even offer less than one frame for the full encoding-decoding cycle.
• Constant quality through encoding/decoding generations: JPEG 2000 maintains the quality after multiple compression steps (see Figure 2) and it is robust to pixel shifts.
EMERGING STANDARDS
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99