Questions about lossless compression

[Parchiao]

Can someone help me understand lossless compression?

I know that there are a couple of lossless compression methods available for videos, see this link.

What is the file format output after you have run the compression? If I want to convert the compressed file to some other format, what do I need?

[Parchiao]

Anybody here knows anything about lossless compression?

[jaegersing]

Not much lah, because it it's not that useful for most people. Usually, need to have more compression to reduce the file sizes, but lossless is limited to around 2:1 compression. Great for archiving critical data that must be restored bit-for-bit.

File format after the compression could be avi or mov (actually these are not really file formats, they are just wrappers which tell the OS how to play them using a codec on the system).

If you want to convert the lossless file to another format you can use virtualdub or any video editing software.

May I know what you are thinking about using lossless compression for? I'm also interested in learning new things.

[Parchiao]

AVCHD.

Read that it will be easier to convert the AVCHD file formats to something else and then convert to the final format that I need.

[jaegersing]

Hi Parchiao. AVCHD is very highly compressed, this is a different subject from lossless compression, right???

The latest Vegas 7 will accept AVCHD files, but the playback is very jerky and unresponsive. The first thing I did when I had to work with AVCHD was export in a different format that is easier to view and edit. I think it will be a couple of years before mainstream PCs will be able to work well with AVCHD. It will take a combination of faster processors and optimised software.

[Parchiao]

I have a core duo processor plus 2GB ram laptop that managed to convert the AVCHD files to MPEG2 format via Adobe Premier Elements with no added effects.

What format did you export your file to?

[Limsgp]

Just wondering.. which camcorder will output files that undergone lossless compression, or rather, uncompressed data?

From what I'm aware of, DV, MPEG2 etc are all lossly compression. The different is only intra-frame or inter-frame. Is there really such thing as lossless compression for video or uncompressed video format?

appreciate any info.

Originally Posted by jaegersing Not much lah, because it it's not that useful for most people. Usually, need to have more compression to reduce the file sizes, but lossless is limited to around 2:1 compression. Great for archiving critical data that must be restored bit-for-bit. File format after the compression could be avi or mov (actually these are not really file formats, they are just wrappers which tell the OS how to play them using a codec on the system). If you want to convert the lossless file to another format you can use virtualdub or any video editing software. May I know what you are thinking about using lossless compression for? I'm also interested in learning new things.

[jaegersing]

Originally Posted by Parchiao I have a core duo processor plus 2GB ram laptop that managed to convert the AVCHD files to MPEG2 format via Adobe Premier Elements with no added effects. What format did you export your file to?

I used WMV when I just needed a file for viewing, but for editing I used Cineform (from Vegas) and Canopus HQ (from Edius).

[jaegersing]

Originally Posted by Limsgp Just wondering.. which camcorder will output files that undergone lossless compression, or rather, uncompressed data? From what I'm aware of, DV, MPEG2 etc are all lossly compression. The different is only intra-frame or inter-frame. Is there really such thing as lossless compression for video or uncompressed video format? appreciate any info.

Hi Limsgp. Yes you are correct, DV and MPEG2 are both very lossy formats, with MPEG2 having much higher compression.

Camcorders? Not many, which is why I said that lossless is not normally that useful (for most people). Although I believe you can get uncompressed output from Canon XH-G1 or XL-H1 thru SDI connection.

Another reason for using uncompressed is if you are generating moving CGI images with alpha channel, and want to maintain high quality for video overlay. AVI files can't usually provide alpha channel unless uncompressed, although Quicktime is more flexible and has some compression options with alpha support.

For high quality compression where you need to reduce the file sizes (a bit) but don't want to tolerate any degradation, lossless compression can be used. There are Huffyuv and Canopus Lossless codecs (among others) that will do this. Canopus HQ and MJPEG are lossy but can still produce high quality results.

[Parchiao]

Originally Posted by jaegersing For high quality compression where you need to reduce the file sizes (a bit) but don't want to tolerate any degradation, lossless compression can be used. There are Huffyuv and Canopus Lossless codecs (among others) that will do this. Canopus HQ and MJPEG are lossy but can still produce high quality results.

Would I be right to say that if I convert the AVCHD format via lossless codecs like Huffyuv to some other format like AVI, then work on the AVI file, it will be less taxing on my PC as there will be less of a need to process highly compressed files like AVCHD on the fly? Will this cause any degradation to the video or sound quality?

[jaegersing]

Originally Posted by Parchiao Would I be right to say that if I convert the AVCHD format via lossless codecs like Huffyuv to some other format like AVI, then work on the AVI file, it will be less taxing on my PC as there will be less of a need to process highly compressed files like AVCHD on the fly? Will this cause any degradation to the video or sound quality?

Hi Parchio. Yes, totally corrrect. That's the whole reason people are using intermediary codecs for HDV editing, and it is even more attractive for AVCHD work. The drawbacks are the extra conversion stage to produce the intermediary files and also the huge file sizes involved. The benefits are reduced processor loading, and that you can go through more generations of rendering without degradation, compared with editing in native HDV or AVCHD.