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This page last updated on Friday, October 13, 2006 at 6:45:58 AM

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MPEG Encoding - the Effect of Different Bitrates

Whilst trying to ascertain what bitrate to encode sub-TV's MPEG movies at, I encoded many different versions of the same AVI file to see what it would look like.

The less the original AVI is compressed, the better, as an MPEG encoded from an Indeo encoded AVI looked awful, whereas a Cinepak file leads to much better results.

The dimensions of all the encodings are 160x120 (actual size shown). The MPEGs are all downloadable.

This was encoded at 100kbps video, 64kbps audio, and weighed in at 1.24M.

Far too big a file for such a small frame!

sub-TV Image

Next up we have a clip at half the video bitrate with the same audio rate (50/64 kbps).

This halved the file, now at 640k.

If the audio bitrate was halved, this saved just over 40k - at 32kbps the file size was 597k.

Taking drastic measures, I dropped the video rate to 8kbps, the audio at 32kbps and all B-frames are being skipped.

If the audio is set any lower it sounds awful, and it seems that the eye has more fault tolerance than the ear, something employed by RealVideo.

The MPEG 'blocking' effect is now making itself apparent but the clip is still watchable. The size of this one is 134k.

sub-TV Image

Then I just went crazy-ape-bonkers and brought the video bitrate down to 4kbps (all other settings same as in the previous movie).

However, my copy of Windows Media Player refused to play the end of the clip, and clipped it. Xing MPEG player coped fine.

Sure looks like RealVideo to me :-)

This one is 91k - I think, for the extra few k, it's worth encoding at 8kbps.


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