FORUMS: list search recent posts

Best orig format - help me choose?

COW Forums : Compression Techniques

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Tom Brooks
Best orig format - help me choose?
on Dec 19, 2006 at 2:13:17 am

I am to shoot a talking head for a corporate client that needs to go to iPod, web video, and DVD. I have a Panasonic HVX-200. Strictly shooting DV tape, which is best origination format for this combo-- 60i, 24PA, or 30P? If you'd like to comment on this also, would there be an advantage to shooting one of the P2 modes for this combination of outputs? Thanks.
-Tom

Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


Return to posts index

Tom Brooks
Re: Best orig format - some tests
on Dec 19, 2006 at 11:55:31 am

I have tested a short sequence of same content (a still object on a studio background)C in 24PA and 60i. Compressed to iPod video and m2v.
Settings for iPod video were the standard setup in Compressor 2.3 (Frame controls automatic, output fields same as source, avg data rate 600kbps).
Setting for m2v is the standard 90 Min. Best Quality 4:3.

Comparing the two iPod versions, the 60i has better resolution, seen as less jaggies on diagonal and curved smooth edges. The 60i version has some dark edges that look like a higher detail setting in the camera and seems to have darker blacks overall. The 24PA version is smoother, less of the dark detail edges, more open in terms of rendering values. Judging which is better, I'd have to say it's almost a draw. Each has its advantages, but the difference in the resolution is disturbing and a drawback of the 24PA. Items like the edges of glasses are going to be noticeably more jaggy in the 24PA version. The data rates were reported by Quicktime player as 600kbps for the 60i version and 360kbps for the 24PA version (both were encoded using the setting which specifies 600kbps). I may try again and attempt to get the same total file size for both versions and see how the 24PA holds up in that comparison. I can't be sure where the difference in the black levels (call it gamma) is coming from, although I assume it's in the camera rather than the encoding process.

Comparing the two m2v versions, the same applies to the rendition of blacks or the overall gamma curve. The 60i version has darker blacks, more contrast, but there's a dark edge that just doesn't show up in the 24PA version. There is no major difference in resolution! Again, the 24PA version looks smoother in terms of rendering values (call it the gamma curve if you will). The data rate is the same for both versions--around 6mbps. Apparently, the encoder for MPEG does a different compensation to get the same total data rate even with a difference in frame rate per second. Which is better in this case? There is no clear winner in terms of judging the quality of the image between the two. If I were to lean one what it would be toward the smoother, more film-like look of the 24PA. That's strictly looking at the image quality and not factoring in issues of motion quality due to the 24fps. My mind tells me that the 24PA should look somewhat better because it is using the same amount of data to produce fewer frames--thus, each frame should contain more data and should look better. To my eye however, the difference is very slight.

If anyone has any commment on this analysis, I'd like to hear it.


Return to posts index

Charles Simonson
Re: Best orig format - some tests
on Dec 21, 2006 at 5:00:14 pm

I don't know what your camera is doing on to create a difference in the quality of the 60i vs 24p, but if all things were equal from that end, then I would suggest to shoot 24p. Since you are going to iPod, web, and DVD, for two of those formats progressive encoding is the only choice, and generally for MPEG-2, progressive sources encode much better than interlaced sources. By shooting at 24p, you will be able to provide more bits per frame than you will at 60i or 30p during encoding. For iPod encoding, I would also suggest trying a different encoder. I have become infatuated with the x264 codec implementation in a very affordable app called VisualHub. Give it a try and I think you will be very satisfied.

As far as the MPEG-2, Apple's encoder is doing the right thing by assigning the same number of bits per second to each encode, and because one format is 24p, you should be getting better results.


Return to posts index


Tom Brooks
Re: Best orig format - some tests
on Dec 21, 2006 at 5:55:22 pm

Charles,
Thanks for the input. You confirm what I thought in general. Yeah, I don't know what's up with the iPod encoding of the 24P. It looks like the result you get when deinterlacing is done by simply throwing away one field. The 60i version was much smoother and higher res, using the default settings of the iPod setting, which does create progressive output. As you suggest, the MPEG-2 looks somewhat better in 24P and doesn't lose resolution like the iPod setting does. There also may be issues with the camera doing things behind the scenes. Looks like the 24P setting could stand more detail, for example. Again, thanks.
-Tom


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]