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MPEG-4: Optimization of Picture Quality and Data Rate

Low Resolutions: Better With Slow Motion Codec!

The same sequence prepared with the slow motion codec. Artefacts occur especially in the transitions of individual people.

Our test clearly establishes that if video sequences are prepared up to a resolution of 352 x 288 pixels (half PAL resolution), then the slow motion codec is definitely better suited! In this range, the video quality of the slow motion codec is better in spite of a lower data rate than with the fast motion codec with a higher data rate. The situation is completely different if the resolution exceeds 352 x 288 pixels. In this case, the fast motion codec should be used, irrespective of the film content (fast or slow movement). By way of a test sequence, we used the DVD video "The Jackal", which was coded up to 720 x 576 pixels with different resolutions. Especially with a full PAL resolution it was shown that the fast motion codec produces very good video pictures with a relatively low average data rate.

Video ResolutionMPEG-4-Codec, Data RateOverall Data RateQualityLength of Film on CD-R
720 x 416 PixelsFast-Motion, max. 6000 kBit/s145 kB/svery good83 min
720 x 416 PixelsFast-Motion, max. 900 kBit/s128 kB/sgood94 min
720 x 416 PixelsSlow-Motion, max. 6000 kBit/s216 kB/svery good55 min
720 x 416 PixelsSlow-Motion, max. 900 kBit/s128 kB/ssatisfactory94 min

This table compares the two MPEG-4 codecs with a full PAL resolution. The slow motion codec produces a higher data rate with high resolutions than the fast motion codec.