Review: Canon XA25, Part 2--AVCHD Image Quality and WiFi Capability

On a Mac, the MP4 file is much more accepted and movie icons populate folders easily and quickly. It also avoids the labyrinthine AVCHD folder structure and places the video files in the same folder as the still images. This makes organizing and managing your media much easier, especially if you use a Mac.

But does the MP4 codec deliver the same visual quality as to the much more universal AVCHD?

In comparing the image to my Panasonic GH2, which netted very favorable opinions in Zacuto's Great Camera Shootout, I was pleased to see that the image held up quite well. Neither the AVCHD nor the MP4 compression proved too heavy-handed.

I was not able to easily discern the difference between clips shot with one codec or the other. If it weren't for the voice over I used during testing, the clips could easily pass as each other.

Unfortunately, nothing seems to stack up to the in-camera compression in the Nikons, which make it look like there's not any compression going on at all despite using even lower data rates than the Canon or the Panasonic.

If it weren't for the moire, aliasing, overall blurry image, and other issues I found in my D800 review, I'd really like it. But it really goes to show how good compressed video could look if care is taken in the camera.

When you gain up, the limitations of using a small sensor with only 2.9 effective MP show up quickly because the camera does not have the large sensor area, or the 15 MP of the GH2, or the 36 MP of the D800. This huge number of pixels allows the processor to "bin" pixels, grouping several of them together as if they were one larger pixel. So if there is individual pixel noise, then it is effectively masked by the other pixels with clean signal.

Where the limited data rate of the XA20/25 comes into play is when you switch to 1080p60. Instead of p24 or p30, you are literally doubling the number of frames, but not doubling the amount of data available to record those frames. For instance, if you use 1080p24 at 24 Mbps, that's 1,000 bits for every frame--and you’re using a longGoP (group of pictures/frames) codec which makes it even more efficient.

Step up to 1080p30 and that 24 Mbps offers 800 bits per frame. But bump the camera up to 1080p60, and you can record at 28 Mbps in AVCHD. This offers only 467 bits per frame—just more than half the data rate of 1080p30 at 24 Mbps.

Using MP4, the camcorder raises the bitrate to 35 Mbps. So 1080p60 spread across 35 Mbps MP4 gives you 583 bits per frame. A 20% increase over AVCHD, but still nowhere near the amount of data available to you if you shoot 1080p30, or 1080p24 with either AVCHD or MP4. So, unless you need 1080p60 for a specific reason—say, for footage you will slow down to provide a "slow motion" shot in a 1080p24 timeline, I recommend shooting with the lower frame rates, and lower data rates, because more data is available for each frame, and that means less compression artifacts in the frame.

In my very basic testing, I could easily see the artifacts visibly increase in my very basic test shot when I used 1080p60. If you have more motion, more detail, and more camera movement, you could easily overwhelm the ability of either the AVCHD or MP4 codecs to deliver clean footage.

Remember, the XA10 and the XA20/25 started their life as consumer camcorders in the VIXIA line. These are high-end camcorders, but they are not built as professional camcorders. This means a more menu-driven workflow, and more data-limited bit rates. But as we have seen with even the inexpensive GoPro Hero, if the content is worth it, broadcasters will air it.