Home > Main > Why h.264 doesn’t equal h.264

Why h.264 doesn’t equal h.264

Since purchasing my Canon PowerShot SX1 I’ve been reading stuff online about how people are touting the superior video capability of cameras like the Canon 5d Mark II or the forthcoming Canon 7D over AVCHD cameras in part because cameras like the Canon’s use 42 Mbps h.264 compression as opposed to the 17 or 24 Mbps compression used in AVCHD cameras.

Now, to be clear.  There is no question that under the same conditions that Canon 5d Mark II, the Canon 7D, and even the Canon PowerShot SX1 take superior video to the AVCHD-based HF10 (which is the model that I’m comparing it to).  I’m just not sure it has as much to do with Compression as it does with optics and sensors, and here’s why.

h.264 is the codec, but it has different levels and profiles that control how things are encoded.  There are many different profiles and levels for h.264 that control complexity, bitrates, etc.  For most people’s purposes, three profiles are of interest:  Baseline, Main, and High profile.  One concrete example of the difference is the Main profile uses B-frames in encoding, while Baseline does not.

So the h.264 coming off of the PowerShot SX1 is Baseline profile, Level 5, while the video coming off of the HF10 is High Profile, Level 4.0.   Needless to say, it takes a lot more power to playback the more complicated High Profile footage (even though it’s a lower bitrate) than it does to playback the higher bitrate Baseline profile footage.

My guess is that its significantly cheaper to put in hardware that will encode in real time into baseline profile than it does to put in hardware that will encode in high profile and since on a digital camera Canon is envisioning different use (short clips as opposed to long sequences) it figured higher bitrate lower profile would be preferable (and I think they were right).  But in the end I think it has more to do with optics and sensors than compression.

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