Captured 20GB AVI from VHS - Any way to shrink losslessly?

[ikaracolt]

Hi,

I am capturing some VHS using a USB capture dongle and Roxio Media Creator Software.
The quality I can get by capturing at the highest 'DV' setting is about what I hoped for.

I was a little surprised that the resulting AVI file for a 90 minute film was over 20GB though...

Is there any way of reducing the file size without losing any of the information - i am used to the simplicity and power of the FLAC format for music and am looking for a video equivalent.

I am NOT interested in fitting them onto a DVD or any particular size, just looking to save space. The conversion must be reversible though - I want to keep these files for a long long time.

Thanks


Thanks.

[johns0]

Dont convert to any other format if you need the original quality since any re-encoding will reduce it and can't be reversed to the original state.

[Verify]

DV is ~14GB/hour so 20GB sounds about right for 90 minutes.

For lossless compressionsee: http://compression.ru/video/codec_comparison/lossless_codecs_en.html

About the best that you can expect is 2:1 on average.

For long term storage, make sure that the storage media is going to last and that you will be able to de-compress later!

[ikaracolt]

ok thanks for the quick replies and i am glad to hear that 20GB is about right.

I will not convert, but should be able to compress and get the files down to around 60% of their size.

I store everything I care about on two different internal hard drives at the moment, so am mechanically ok, but vulnerable to fire and theft...

Would Virtualdub be the best software to compress within? the options in Roxio are rather limited...

[DB83]

But you said that you want the process to be reversable. Check the comments made by Johns0. Once you compress you are actually converting. And that conversion is not reversable. That is to say you can return the file to its original size but you will not have the same video quality as the original.

[ikaracolt]

Oh.

I was drawing a distinction between conversion and compression, but it seems that any change is irreversible...

I have spent ages working with Vinyl/Cassettes and CDs and know you can change WAV and CD-audio to FLAC and back again without loss, i guess that video is more complex than audio...

I guess I shall have to get some more disk space...

Thanks all.

[Gavino]

Once you compress you are actually converting. And that conversion is not reversable. That is to say you can return the file to its original size but you will not have the same video quality as the original.

But lossless compression is completely reversible, just like FLAC for audio or zip for general data - that's the whole point of it.

However, lossless compression only applies when the starting point is uncompressed input.
DV is already compressed by about 5:1, so to convert that to something like HuffYUV will actually make it bigger.
Moreover, that conversion (decompression of the DV before lossless compression) is not reversible (was that what you meant, DB83?)

The audio analogy would be converting MP3 to FLAC.

[DB83]

Once you compress you are actually converting. And that conversion is not reversable. That is to say you can return the file to its original size but you will not have the same video quality as the original.

But lossless compression is completely reversible, just like FLAC for audio or zip for general data - that's the whole point of it.

However, lossless compression only applies when the starting point is uncompressed input.
DV is already compressed by about 5:1, so to convert that to something like HuffYUV will actually make it bigger.
Moreover, that conversion (decompression of the DV before lossless compression) is not reversible (was that what you meant, DB83?)

The audio analogy would be converting MP3 to FLAC.

Indeed. But the OP is talking of compressing,converting, call it what you will, his DV capture by 60%. To do that he will be using lossy codecs and will not be able to reverse that process and retain the quality of the original DV.

[Verify]

Silly me, I was correct on the DV file size but forgot that lossless compresion is for uncompressed video data. For more discussions see:

https://forum.videohelp.com/threads/304905-FFV1-does-not-shrink-the-DV-size

https://forum.videohelp.com/threads/258985-Lossless-compression-CODEC-for-archiving-DV25-MiniDV-Files

http://www.tomshardware.com/forum/144531-33-best-lossless-compression-files

among others.

[ikaracolt]

OK Thanks guys - the fact that my video is already compressed ~5:1 explains pretty clearly why i can't move it around losslessly or save any more space for free - I had overestimated my starting point significantly.

Thanks for making the posts required to get to the bottom of my misunderstanding.