5D Mark II vs 7D video bitrates: Does it matter?

Started Sep 15, 2009 | Discussions thread
pgb
pgb
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Re: 5D Mark II vs 7D video bitrates: Does it matter?
In reply to austinphotog, Sep 16, 2009

austinphotog wrote:

cws2882 wrote:

Very very interesting. I am looking into both cameras for video. I would think higher bitrate is always better when dealing with compressed audio or video. 50% improvement should be noticable.

There is a lot of artifacting on the 5DII, I'm not sure how much of it has to do with the bit rate. The higher bitrate should help reduce motion artifacting.

I was thinking to myself why anyone would want 24hz when recording if you can get 30hz and set the shutter speed to give a smooth or sharp look to it. I guess higher bitrate per frame would be one reason for this.

Yes there's a bit of a love affair with 24fps. Most television broadcasts of sports use 50i so that the judder is tolerable. The faster the frame rate the better fluidity of motion. There's also an advantage shooting at the mains frequency to avoid strobe flicker from the AC lighting. If your going for an international TV sale or laser recording to film use 24 otherwise use the frame rate that matches the local TV system. There would be a compression advantage
as stated shooting less fps.

24p is the framerate that movies are shot and shown in. This gives a certain look. There are 3 reasons you may want 24p - 1) you want the look of cinema, 2) you want to show it through movie projection, and this allows the least artifacting when transfering to film, 3) it allows for a slower shutter speed but the better iso performance doesn't make this as necessary.

Where did you get this data from?

Eug wrote:

The 5D Mark II has a 38ish Mbps video bitrate for its 1080p30 H.264 .MOV QuickTime video files.

The 7D has an even more remarkable spec of about 47ish Mbps for its 1080p30 files. That's a 20-25% improvement in bitrate.

Also Canon claims the bitrate for 1080p24 on the 7D is similar, which means potentially a whopping 50% improvement in effective bitrate per pixel. (There is no 1080p24 mode at all on the 5D2.)

Do you think that actually matters though?

If your not going to compress it again these bit rates would be tolerable. If you
broadcast your putting it through a MPEG2 compressor at around 40:1, likewise
BR DVD, then the low origination rate could become an issue. Internet delivery
is even more of a compression issue.

Fast moving action or camerwork with little frame redundancy also falls apart quicker at these lower
bit rates. Step through a fast camera pan on a DVD, it's heaps worse than
analogue video.

For 1080p30 H.264, 38 Mbps is already a very good bitrate.

yes it is. HD DTV is only 20mbps at most and this is the older MPEG2 codec.
H264 is about twice as effiicent so 38mbps h264 would be about 4 times
less compression than HD TV BUT see above ...

BTW, for comparison's sake AFAIK most recent AVCHD camcorders are about 24 Mbps H.264, and HDV is only about 25 Mbps MPEG-2.

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