crop without recompress?

[previn]

Is it possible or is there any software that will enable me to crop from top and bottom of avi file without having to recompress video? I have a file which is about 20 mb too big for cd, I don't want to lose quality and there is nowhere to cut video. As aspect ratio is 4:3 and I have wide tv I could cut top/bottom off to view on my standalone divx player. Is it possible?.

Ta

[Tommyknocker]

Sorry, cropping will not reduce the size of your video. The only ways to do it is to shorten the time of the video, or lower the bitrate. I cannot tell you how to do either without re-encoding.

[previn]

Ok, I might be being stupid here but I would have thought that if you reduced your picture size by 20% then you could reduce the size of your encode by 20% for the same bitrate?

[FulciLives]

Ok, I might be being stupid here but I would have thought that if you reduced your picture size by 20% then you could reduce the size of your encode by 20% for the same bitrate?

Well yes and no

The size in MB or GB etc. of a video file is determined by the running time and the bitrate used. Resolution means nothing as far as that equation goes. So a 120 minute movie at 720x480 (full NTSC DVD resolution) is the same size as a 120 minute movie at 352x240 (NTSC VCD resolution) when using the same bitrate.

However here is how the SIZE of the image DOES play into things ...

The lower the resolution the less bitrate you can use to get a decent image. For instance the best you can do at 720x480 is about 8000kbps but Half D1 resolution (352x480) hits the MAX bitrate at about 5000kbps. So pushing the bitrate above 5000kbps for Half D1 makes no sense yet Full D1 (720x480) needs 8000kbps to look "best".

Now let's take a really "low" bitrate. Say 3500kbps. At Half D1 this will look good even though it is less than the MAX for Half D1. But Full D1 at 3500kbps will not look good at all ... at least it will be noticeable less in quality.

So again using 3500kbps at Half D1 and Full D1 will create the same size file but the Half D1 encode will look better than the Full D1 encode.

Hope that makes sense

- John "FulciLives" Coleman

[previn]

Perfectly, Thankyou I am now enlightened!

[FulciLives]

Perfectly, Thankyou I am now enlightened!

Just remember that Full D1 has a higher resolution than Half D1 so sometimes a Half D1 encode will look slightly "soft" if you were to compare it to the same source encoded at Full D1.

However for most source material the Half D1 resolution is good enough for your standard TV and since it allows you to use a lower bitrate YET still achieve a quality image ... well now you see the benefit.

VCD resolution though (352x240 NTSC or 352x288 PAL) is way too low of a resolution to look truely good even if you use a very high bitrate. The lack of resolution is just a killer on the image when you blow it up to fit your TV or your computer monitor.

- John "FulciLives" Coleman