Video: source quality and encoding speed

[obiwan71]

I've made a test which leads me to think that encoding speed depends a lot on the quality of video source. It seems that encoding speed greatly decreases when source is bad/poor quality.

The codec used was DivX 5.0.3. No filters were applied.

Both sources are videos captured with my DC10+.

1st encoding: clean MPEG-2 source - file was encoded from a satellite MJPEG capture.
Screenshot: http://sbouf.free.fr/screenshot_bridget_jones.jpg
AVS script: http://sbouf.free.fr/bridget_jones.avs
Encoding speed (thanks to my new processor :)): http://sbouf.free.fr/vitesse_encodage_bridget_jones.jpg

2nd encoding: MJPEG TV capture - medium quality.
Screenshot: http://sbouf.free.fr/screenshot_capture_hertzien.jpg
AVS script: http://sbouf.free.fr/capture_hertzien.avs
Encoding speed: http://sbouf.free.fr/vitesse_encodage_capture_hertzien.jpg

[ppera2]

Odd pixels after crop... cc...

It's well known what you posted. Noise is main enemy of compression.

[obiwan71]

It's well known what you posted. Noise is main enemy of compression.
I know. In fact I was just wondering about the GREAT influence that picture quality can have on encoding.
Besides, I've been a little surprised with the tests I've done recently with my new PC. Encoding is really fast (Athlon XP 2600+), but I thought it could be even faster (:D) in some cases: with my previous PII, the average encoding speed could reach 13 or 14 fps when compressing low-resolution videos (384x288), including noisy source, and as far as I can remember picture quality didn't seem to have such influence on speed encoding. :confused:

[obiwan71]

I've installed PICVideo MJPEG Codec, and encoding takes much less time. :eek: So speed encoding seems to depend directly on the decompressor used by VirtualDub or AviSynth. To use the software codec to import videos into VirtualDub, I just have to choose PICVideo MJPEG Codec as "Primary MJPEG Codec" during setup, and it works quite well. But that way PICVideo MJPEG Codec is also used as the encoder.
Is there a way to use the PICVideo codec as a decompressor/decoder only?

I've just read part of this interesting thread:http://forum.doom9.org/showthread.php?s=&threadid=53622&highlight=Picvideo

[obiwan71]

Everything is OK now! I've installed the Morgan codec and it's great. I can go on capturing with the DC10+ codec while decoding captures with the new codec. It works very well... :)