24p via 60i, what a pain in the ass!

loocas | opinions,software,technical | Thursday, August 20th, 2009

Why is it such a big deal to make a consumer level camera (hell, even some pro-sumer level ones) that does a true, native 24p video?

I have a VIXIA HG20 that records everything via its 60i mode. I have no idea why, or what was the technical reason for this, but it’s a pain!

Ultimately, when I record at the 30p mode, I get a 29.97 progressive video (no fields), however, when recording at 24p, I get interlaced 29.97 embedded in the 60i mode! WHAT THE HELL? Well, no big deal, I thought, I’ll record everything at 24p (via 60i) and have it converted to the regular 24p. Well, it would be a good idea if the software I run here worked as advertised! For instance, ProCoder 3 has a known issue decoding native 1920×1080 AVCHD video (it has no problems with 1440×1080 with the 1.33 PAR though), so I can’t use that, not directly at least. Which sucks real bad as ProCoder can apply pulldown filters and generally does a pretty good job of removing fields.

So, I had to use Adobe Media Encoder, that reads the 1920×1080 AVCHD perfectly fine, but, on the other had, has problems removing fields! So I exported the embedded 29.97 interlaced footage in a file sequence (I have no idea if this is the right way of doing things, not sure if the AVCHD container treats fields in a different way than simply writing down each single file with odd/even lines “messed up”, so, if you know better, please do let me know in the comments below), then I took this sequence and fed ProCoder with it. Setting up the input parameters properly is the key. Then I applied the Pulldown filter and specified another output, this time I set it to 24 progressive and exported.

The resulting footage looks crisp and doesn’t suffer from repeating frames (like when exporting via Media Encoder). However, this way, I’m not 100% sure I’m keeping the proper timing of the original footage, since the sequence only looks to be fine to me, but technically? I have no idea! :( I’ll have to investigate further, but generally, this is a real pain in the ass for non-video dudes (like myself) that only want to shoot footage for later post-fx manipulation/treatment.

There are also some more severe problems like the rolling-shutter distortion that all CMOS cameras suffer from (even RED!), which is another story… But basically, there’s no way I could affort to buy a film camera and scan it every time for the proper workflow

2 Comments »

  1. hdmi and sdi require it to be transported over the cable as 60i, thats why cameras do this.

    Comment by Deke Kincaid — August 21, 2009 @ 22:19

  2. Thanks for the clarification, Deke, I appretiate it.

    Comment by loocas — August 21, 2009 @ 22:33

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