Quality assessment of MPEG-2 encoded sequences

Methodology

The Degradation Category Rating (DCR) subjective test methodology has been used - see ITU-T P.910 for additional details.

32 pairs of original/impaired sequences have been presented to each subject (corresponding to 8 different video sequences encoded at 4 different bitrates each).

Test participants

23 individuals have participated in this test. The participants were male and female students with ages in the range from 23 to 25 years old.

The subjects were screened for normal visual acuity and color blindness. One of them showed color blindness.

Test room environment

Two LCD displays of the same model have been calibrated. The display and room characteristics used in the subjective tests are listed below:

  • Height of the picture shown in the screen: 8 cm
  • Viewing distance: 64 cm
  • Background room illumination: 13.45 lux
  • Peak luminance of the LCD screen: 95.8 lux
  • Luminance of inactive screen: 2.23 lux
  • Luminance of background behind the display: 10.15 lux
  • Ratio of luminance of inactive screen to peak luminance: 0.023
  • Ratio of luminance of background behind the display to peak of luminance: 0.14

Encoded sequences

The original sequences were encoded using the MPEG-2 codec developed by the MPEG Software Simulation Group (MSSG).

The main encoder parameters were as follows:

  • Main profile, main level
  • GOP structure: 15 frames length, with two B frames inserted between I/P frames
    IBBPBBPBBPBBPBBIBBP...
  • Intra DC precision set to 9 bits
  • Rate control provided by the software

A template for the encoder configuration file can be found HERE.

Data

You can get all bitstreams for this test HERE.

MOS data is HERE.

Notes:

  • Sequence "Australia" 
    Only the first 250 frames were actually used (and displayed at 25 frames per second);
  • Sequence "Mobile"
    A sequence of 900 frames     that result from merging Mobile sequence in the forward direction, then backward, and then forward again has been encoded. From the resulting sequence, only the last part (last 300 frames) has been used for subjective quality assessment.