MPEG-4: Optimization of Picture Quality and Data Rate

Compromise: Quality Vs. Resolution

This table shows the increase in the data rate depending on the chosen codec and the respective resolution. Furthermore, instructions are given for writing a DVD video onto a CD-ROM depending on the respective CD-R.

Especially in the case of DVD videos that have a playing time of more than 90 minutes, it is often the case that the storage capacity of a CD-ROM with just under 700 MB (CD-R80) is not sufficient. In order to avoid having to split the DVD video onto two CD-ROMs the average data rate should be reduced when carrying out the MPEG-4 encoding. In principle, there are two different ways of doing this. On the one hand, the resolution can be slightly reduced or, on the other hand, you have to marginally sacrifice picture quality, so that the data rate is lowered with a consistent resolution.

The following screenshots taken from our test sequences show the extent to which the different resolutions affect the average data rates.

All three video sequences were prepared with the slow motion codec and different bit rates. While the lowest resolution only requires 250 kBit/s, the resolution with 352 x 224 pixels needs as much as 700 kBit/s.