FFV1 does not shrink the DV size

[dywillnerd]

Hi,

I have a DV which is about 3.x GB. I try to compress it
with FFV1. I was expecting it to be compressed down to
about 1.3 GB. But I keep getting about 5-6GB.

I use the Supper and also the VirtualDub with ffdshow.
Both give me the same result. Can someone shed
some lights on this?

Thanks.

Duncan

[poisondeathray]

FFV1 is a type of lossless compression, it's not supposed to shrink the filesize

If you wanted to shrink the filesize, you would pick another format, but there will be quality loss.

What are you trying to do?

[dywillnerd]

poisondeathray,

Thank for reply. I read about that the FFV1 can compress as much
as 1/3. What does that mean?

I simply want to archive my file so that it does not take up too
much storage spaces. The DV is downloaded from Camcorder.
I thought I should be able to compress it without losing any
quality.

Do I mis-understand the so called compression rate?

Thanks.

Duncan

[poisondeathray]

I read about that the FFV1 can compress as much
as 1/3. What does that mean?

That would be ~1/3 compared to uncompressed RGB , so that is still larger than the original DV

All forms of commonly used video lossless compression will make your filesize larger (e.g. lagarith, huffyuv etc...)

You can use archiving software e.g. winrar, winzip, 7-zip and it will take ~10% off, but it's is rendered useless until taken out of the archive

Or you can use lossy compression formats (quality loss) like AVC, MPEG2, XviD etc.. and compress it much more, at the expense of quality loss depending on how much compression you use

If you are archiving, most people suggest getting extra hard drives and keeping the DV-AVI format. You can search, there has been several threads on archiving DV and other video formats, with pros/cons/alternatives/costs discussed

[dywillnerd]

poisondeathray,

Thanks for the reply. So why should them larger than the DV?

[jagabo]

The process of converting from one codec to another involves decompressing the source then recompressing with the new codec.

DV is about 13 GB/hr. Uncompressed RGB is about 112 GB/hr. If a codec claims it can reduce the size to 1/3 of the source, they mean 1/3 the size of an uncompressed video. 1/3 of 112 GB is about 37 GB. So a DV video is expected to get ~3 times larger. Roughly the ratio you are seeing.

Note that exactly how much compression you get with lossless codecs depends on the nature of the video. An all black video with no noise will compress down to almost nothing. Inter station static will hardly compress at all.

[dywillnerd]

jagabo,

Thanks for reply. This is very educational.
So. Since DV is the source, the uncompressed RGB can't
have better quality. If we reverse the process, are we
saying DV has the highest compression rate?

* I guess I need learn more about the process, any
suggestion on good literature?

Thanks.

[jagabo]

Yes, DV usually has a higher compression rate than lossless FLV1. But DV will always be 13 GB/hr. FLV1 will vary depending on the particulars of the video.