Use same computer for video editing and capturing?

[sirbyron]

Quote:

Originally Posted by sanlyn

YUY2 is a colorspace matrix. huffyuv is a lossless compressor that can compress YUY2 or RGB video.

Capture from SD VHS to lossless huffyuv compressed YUY2 runs about 25GB per hour of video. Un compressed YUY2 would be about 75GB per hour.

If you want Virtuadub capture to huffyuv YUY2, set the desired colorspace to YUY2, set the compressor to huffyuv.

So running huffyuv YUY2 is good enough capture for editing VHS tapes? No need to do the "uncompressed YUY2"? These vids are approximately 12 minutes each I am working on.

[lordsmurf]

Quote:

Originally Posted by sanlyn

lossless huffyuv compressed YUY2 runs about 25GB per hour

It's more like 30-40gb/hour.

Quote:

So running huffyuv YUY2 is good enough capture for editing VHS tapes? No need to do the "uncompressed YUY2"?

It's the same quality. The compression is just filesize, using Juffman encoding (like zip compression). The to are visually indistinguishable.

If you want to get really technical about it, I do think the math takes some minor shortcuts. I have seen some minor differences in the quality, but that was a long time ago (earlier Huffyuv codec versions), and was hard to spot. We're talking miniscule differences on specific kinds of content. I don't know that any of it applies anymore. It's certainly not worth the 2x filesize.

This is what I use. If it wasn't the best, I wouldn't use it.

[sanlyn]

Uncompressed YUY2 AVI video is 100% decoded video frames, 100% of the original image information. Lossless compressors such as huffyuv and Lagarith do not re-encode video -- rather, they're more like ZIP or RAR lossless compression but much faster and specifically designed for video. They compress, but they don't re-encode. What you get back after you decompress lossless AVI is exactly what you put into it in the first place.

Video encoding + lossy compression is a different story. Lossy codecs such as MPEG, h264, XVid, QuickTimne, DivX, etc., involve multilple levels of compression. Video is encodd into Groups of Frames (GOPs), each GOP containing at least one or more key frames. A key frame is the only frame in the GOP that is a complete, 100%, full-sized digital copy of an original frame. The other frame types inside a GOP are not complete images: they contain only data about how the frames have change since the last key frame in the GOP.Moreover, lossy codecs use various levels of additional compression that discard data that the encoder decides is unnecessary, or that the encoder can't accurately maintain at insufficient bitrates. Video encoded with very long or large GOPs up to 250 frames are very lossy encodes that are difficult to edit without serious data loss. Smaller GOPs such as the ~18-frame limit in PAL/NTSC are easier to edit with smart-rendering editors, but they still are encoded in a lossy manner that loses anywhere from 15% to 60% of the data that went into it.

Each modification of lossy video involves lossy re-encoding. What gets lost from earlier encodes is never retrieved. It's gone. Kaput. Nada. Re-encode again, and you lose more. Losslessly compressed AVI as discussed here contains 100% of the original, full-sized images that you started with. But a method of "compression" is used that's more like ZIP, where similar occurrences of data are combined into shorter codes. No data is thrown away.

[sirbyron]

Thanks Smurf and Sanlyn. Great explanation Sanlyn and yes, that makes a lot more sense to me now. Not "exactly" what you are saying but I guess the result of lossy compression works similar to taking a picture of a picture of a picture maybe? You lose more info (detail) with every "copy" you make. Love the info here. Thanx!