DV V MJPEG? help?

[mrtj1]

i use mjpeg now and an hour is about 8 gigs of space. i have a sony digi-8 camcorder and was told that i could enable video in so i could plug my tv into the source and output as DV through my firewire card.

question is:

is it better than mjpeg? what kind of filesize would an hour take at 704x576? and is the quality higher?

[Dr Mordrid]

Better for what? For "normal" footage DV's great, but for sequences where you're doing effects it can pose problems. More on that later.....

The frame size of DV is fixed at 720x480 NTSC and 720x576 PAL. NO adjustments allowed so no half frame captures.

As for the file size; DV's audio and video bitrate are both higher than that of Matrox's MJPeg so the files will actually be a bit larger in terms of megs/minute.

Another issue is that DV has a limited colorspace (4:1:1 for NTSC; 4:2:0 for PAL) compared to most MJPegs which use 4:2:2. This means it has fewer color samples per scanline. They both have the same B&W content. Here's an image to help you visualize the differences;



So, in the grids above (each of which represents a "macroblock") 4:2:2 video would have 24 color samples, 4:2:0 video would have 16 color samples and 4:1:1 video would only have 12 color samples. A macroblock is the smallest compressed region a codec does.

This results in a higher likelyhood of artifacting in titles, overlays and other effects when using DV, especially NTSC DV.

This can be mitigated somewhat by keeping your analog board in the system and capturing from a DV cam's S-Video port when you have a problem sequence. Capturing analog softens the video a bit and masks some of DV's less than spectacular performance with some subjects.

Dr. Mordrid

[mrtj1]

what i capture is tv shows at the highest res i can for making into divx so i can put 1 sometimes 2 45 min eps per cd. 400 megs each. i dont want to do effects, just edit out commercials, crop out black bars i get from my g400 for some reason in the caps and that's about it

[Dr Mordrid]

You'd be better off capturing MJPeg to half D1 (352x480) then encoding it to full frame DivX. That'll cut the capture bitrate in half, doubling your capture time before filling the drive, with little in the way of quality losses. This technique is often used by cable & satellite companies to cut the bitrate of the video they use.

Try it and see how it works.

Dr. Mordrid

[mrtj1]

i am not really bothered by file size that much since i have 162gb of hard disk space in total. but i will try what you said.