AVCIntra vs DVCPRO HD
- Thread starter rc444
- Start date
Barry_Green
Moderator
AVC-Intra is better in all ways. They're both 100mbps and 4:2:2, but AVC-Intra is full-raster (1920x1080, whereas DVCPRO-HD is 1440x1080) and 10-bit bit depth. Plus, the AVC compression is at least twice as efficient as other codecs, so the images look sharper, richer, and less compressed.
^faldo^
Member
From what I know (somebody please shoot me down if I'm wrong) AVC-Intra is based on wavelet compression, which is the next big mathematical jump from the foundations of all the old codecs we used to use (specifically the discrete cosine transformation).
The basis is that you transform the image into a different domain to make it easier to represent with a more simple mathematical function, and hence take up less space.
I wish I knew more about it and could explain it better, but I haven't been taught the crazy maths yet.
More info:
http://www.imageprocessingplace.com/DIP-3E/dip3e_main_page.htm
plus some calculus.
The basis is that you transform the image into a different domain to make it easier to represent with a more simple mathematical function, and hence take up less space.
I wish I knew more about it and could explain it better, but I haven't been taught the crazy maths yet.
More info:
http://www.imageprocessingplace.com/DIP-3E/dip3e_main_page.htm
plus some calculus.
JeganRX
Well-known member
Well I'm not experience in crazy math myself, but AVCIntra is *not* a wavelet codec. It's DCT based like all MPEGs before it (Wavelets will probably be next, but judging by current wavelet codecs - with the exception of redcode, which who knows how it would look at lower bitrates - we have a long way to go). The only difference is exactly in the name. "Intra" refers to intra-frame encoding, which compresses each frame as a unique "piece", if you will. I'm repeating most of what's been said with the whole HDV debacle that started years ago, but inter-frame encoding would be the opposite, encoding whole frames every GOP (Group of Pictures, not Grand Old Party...), while frames in that GOP are referenced to what's called the I-frame.
Think of inter-frame compression as someone trying to rewrite a book from only every 15th page (Since HDV has 15-frame GOPs, AVCHD seems to have avoided much talk about GOPs...), with some parts of the missing pages scattered throughout every 15. Obviously you can see how higher compression is achieved here, as those inbetween frames (P and B frames) can discard large portions of themselves in orded to be referenced to an I-frame. The savings is dramatic with AVC, and a lot less so with HDV (MPEG2), but regardless, offering intra-frame compression means two things:
- Each frame is independently encoded, which means decoders no longer have to reconstruct those inbetween frames from the I-frames (also called key frames). This saves time, as transcoding wouldn't be necessary (in my opinion, transcoding is a terrible option unless to a lossless format, sorry ProRes is nice, but doesn't count in my book; I'd rather just let the NLE handle the interframe decoding natively), and even speeds up shuttling, for the very same reason.
- Intra-frame encoding, provided the bitrate is high enough, will far outshine inter-frame encoding. Now this may sound obvious, as more bits usually does guarantee a higher quality (That's not the rule though!), but it's more related to the fact that each frame is unique, unreferenced to another frame. Don't be fooled by placebo effect though, inter-frame encoding in AVC, particularly at Blu-ray bitrates, will look pretty much the same, so don't buy into intra-frame just because it encodes at a higher bitrate!
- Bonus: Not inherent of Intra-frame encoding, but simply a bonus to the AVCIntra standard that Panasonic implemented, 4:2:2 color space (with AVCIntra 100), and 10-bit color depth (both 50 and 100), this is of course, awesome for chroma keying and color correction, respectively.
Hope that cleared anything up....