Why can I never get decent re-compression? (file size)

[VideoBeginner]

I use VDM, and I either do not know what I am doing or I am expecting too much. I will give my current example, but this seems the case every time.

I start with a video that is 149,495KB, 360x280 (34,103 frames), 25fps, and audio

I then:

Remove all but 8,249 frames (76% reduction)
Reduce video to half size (180x140) w/Bilinear and Interlaced filtering
Use Sharpen filter: 30


So now I have an video image that is far worse quality and 1/4th the length. But testing a few different compressions and settings within them (I really have no idea which is best), I usually end up with a file only about 50% to 55% reduction in file size.

It seems like other videos I have seen recoded end up about the same quality but the file size is reduced significantly (whereas if I did the same, I would probably get a 5% increase in size). Is this because the audio does not compress at all or am I just not doing things right?

[Guest]

Be specific about what compression and settings you use, for both audio and video.

Try Xvid or DivX.

[VideoBeginner]

To be honest, I don't know how to adjust (or even check) my audio compression. The only audio options I have ever found are under "Streams -> Stream List" with Interlacing or removal or replacement of the stream. The help file does not appear to explain where compression options are.

I use full processing mode, and the video codec that I usually try to use is DivX 5.0.2

I usually use DivX 5.0.2 and full processing mode. The settings so far that I have found balancing size and quality is "1-pass; 0 bitrate".


I have looked at XviD MPEG-4 Codec, but there are so many option possibilities, I really don't know where to start.

[Guest]

Right click on the audio stream in the stream list and you will see a popup menu. First select Full Processing Mode. Then do it again and you will get the Compression item enabled which you can then configure.

You can try disabling audio and see if the result is then the size you expect. If so, then you need to compress the audio.

[VideoBeginner]

Well look at that! I never even payed attention to what was written in the greyed out options! :rolleyes:

I have tried removing the audio completely, and obviously that does reduce the size greatly, but that's usually not a valid option. So I will toy around with audio compression.

Thank you very much.

[Guest]

Happy to be of service.

MPEG Layer 3 will be a good choice for your audio compression.

[pandy]

Reduce video to half size (180x140) w/Bilinear and Interlaced filtering
Use Sharpen filter: 30



avoid sharpening after resizing - try to make sharpening before resizing, use something else than bilinear (bicubic perhaps)
if You reduce size in vertical exactly 2 (or 4,6 etc) there is no need to do special interlace processing (it will blend both fields nicely)
sharpening after resizing will hurt compression for sure