Codec Evaluation

Test Conditions

This web page reports the detailed evaluation of the DISCOVER monoview video codec. However, in order to evaluate the DISCOVER codec and facilitate future comparisons against its RD performance it is essential to precisely define the performance evaluation conditions and the video codec control parameters.

Only the luminance component is coded and thus all metrics (e.g. PSNR) refer only to the luminance.

Test Material

The monoview test material used and some relevant test conditions are described in the following:

Since sometimes there are multiple versions of the same sequence (e.g. with different spatial or temporal subsampling filters) you can download each sequence here (already downsampled @ 15Hz):

The sequences at 30Hz can be found here: Foreman, Hall Monitor, Coast Guard, and Soccer

Quantization

In DISCOVER codec, eight rate-distortion points are considered most of the times, corresponding to the various 4×4 quantization matrices depicted here:

16 8 00
8 0 00
0 0 00
0 0 00
32 8 00
8 0 00
0 0 00
0 0 00
32 8 40
8 4 00
4 0 00
0 0 00
32 16 84
16 8 40
8 4 00
4 0 00
Qi = 1 Qi = 2 Qi = 3Qi = 4
32 16 84
16 8 44
8 4 40
4 4 00
64 16 88
16 8 84
8 8 44
8 4 40
64 32 168
32 16 84
16 8 44
8 4 40
128 64 3216
64 32 168
32 16 84
16 8 40
Qi = 5 Qi = 6 Qi = 7Qi = 8

Within a 4×4 quantization matrix, the value at position k indicates the number of quantization levels associated to the DCT coefficients band b(k); the value 0 means that no Wyner-Ziv bits are transmitted for the corresponding band.

The various matrices will be referred as Qi with i= 1, …, 8; the higher is Qi, the higher are the bitrate and the quality.

Slepian-Wolf Codec

In order to perform Slepian-Wolf coding the rate-compatible LDPC Accumulate (LDPCA) codes, which have been introduced in [1], are used. The performance of LDPCA codes are shown to be better than those of turbo codes for moderate and high rates, for the distributed video coding case.

Side Information Creation Process

The creation of the side information has been described in detail in [2]. The most important control parameters related to the frame interpolation in the side information creation process are presented:

Key Frames Coding

The key frames are always encoded with H.264/AVC Intra (Main profile) since this is the best performing Intra video coding standard available. The key frames quantization steps have been found using an iterative process which stops when the average quality (PSNR) of the WZ frames is similar to the quality of the Intra frames (H.264/AVC encoded). The selection of these QP values for the key frames was made with the target to have almost constant decoded video quality for the full set of frames (key frames and WZ frames). It is important to note that investing the same total bitrate in a different way between WZ and key frames may lead to a better RD performance, for example by investing more bits in the key frames, at the cost of a less stable video quality. This is a choice to be made by the encoder knowing the consequences in terms of subjective impact. The key frames are coded with constant quantization parameters and have been obtained for GOP = 2, QCIF@15 Hz as defined in:

Q1Q2Q3Q4Q5Q6Q7Q8
Foreman4039383434322925
Hall Monitor3736363333312924
Coastguard3837373433313026
Soccer4443413636343125

References

1. D. Varodayan, A. Aaron and B. Girod, “Rate-Adaptive Codes for Distributed Source Coding”, EURASIP Signal Processing Journal, Special Issue on Distributed Source Coding, pp. 3123 - 3130, vol. 86, nº 11, Nov. 2006.

2. X. Artigas, J. Ascenso, M. Dalai, S. Klomp, D. Kubasov, M. Ouaret, "The DISCOVER codec: Architecture, Techniques and Evaluation", Picture Coding Symposium 2007, Lisbon, Portugal.