The 2 kinds of AVCHD

[Steve Mullen]

I'm always amazed when I find the answer to a question in something already published -- in this case MY July story on MPEG-2/H.264 in Broadcast Engineering.

The question -- why are some people claiming an 18 Mbps limit for AVCHD and others claiming a far higher value. Turns-out it has nothing to do with the size of DVD nor the spin capability of a player. I quote from myself:

"Like MPEG-2, H.264 has Levels that define frame-size, frame-rate, number of pictures searched, and maximum data–rate. AVCHD uses Level 4 while AVCCAM uses Level 4.1. Sony and Panasonic (consumer AVCHD) use H.264 Main Profile. Canon and AVCCAM use H.264 High Profile. (Blu-ray’s H.264 uses High Profile.)"

Because my story was NOT about AVCHD, I didn't add some additional information. Here are more detailed sentences:

Sony and Panasonic (consumer AVCHD) use H.264 Main Profile at Level 4.0. Canon and AVCCAM use H.264 High Profile at Level 4.1. (Blu-ray’s H.264 uses High Profile at Level 5.1.)

What does 4.0 vs 4.1 vs 5.1 mean -- everything!

First: BD supports 5 Reference frames because it is Level is 5.1. AVCHD supports only 4 because it's Level is 4.0 or 4.1.

Second: Level 4.0 with a MAIN Profile supports a maximum data rate of 20 Mbps while Level 4.1 with a HIGH Profile supports a maximum data rate of 25 Mbps.

What all this means is Sony -- in keeping with it's public stance that AVCHD is a "consumer" format only cares about MAIN Profile at Level 4.0 -- which means a max data rate of 20Mbps. It need support HIGH Profile at Level 4.1 in VEGAS only if it chooses to.

Panasonic has the same stance which is why it's calling it's 21 Mbps HIGH Profile at Level 4.1 -- AVCCAM.

Canon, which has always used HIGH Profile at Level 4.1 is simply extending the data rate to its maximum. Since Canon is aware that Sony and Panasonic need only support MAIN Profile at Level 4.0, it knows there MAY be compatibility issues with some Sony and Panasonic products.

In fact, ANY company that only supports MAIN Profile at Level 4.0 is not going to be able to import 24 Mbps video. And, any device that only supports MAIN Profile at Level 4.0 is not going to be able to play Canon files copied to a DVD.

Thankfully, now that Sony accepts Canon AVCHD, it MUST be able to import 24 Mbps. However, it need not export 24 Mbps.

In a real sense this is like HDV where there were HD1 and HD2. Only the difference was obvious: 720p vs 1080i.

With AVCHD, two companies are calling two specs by the same name.

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PS 1: It looks like in the Vegas Burn-to-Disk, the encoder being is used is Level 4.0 with a MAIN Profile supporting a maximum data rate of 20 Mbps. In other words, the one that would be used to make AVCHD. Likely this means not having to pay for an AVC encoder -- it can use it's own AVCHD encoder.

PS 2: If you create a Main 5.1 file content on red-laser disc -- some BD plays will see this as an error. Or, they will try to play it, but the use of 5 Reference frames in the source will cause stutter. Anything burned to a red-laser disc, must be 4.0 or 4.1. It need NOT be AVCHD.

[Paul Cascio]

Wow, fascinating info. Thanks. Glad I learned this before buying avy AVCHD cameras. Atcually I do a have a cheap Aiptek 1080p, but just as a toy. I'm assuming it's 4.x also?

[Jeff Kellam]

Steve:

In a nutshell, does this mean editing HMC-150 footage in Sony Vegas Pro 8.0c will be problematic or impossible in the highest camera quality setting which I assume is a higher profile and bitrate?

Would there be import or export problems?

Im just trying to decide if the HMC-150 is usable with Vegas.

Currently Im authoring projects downconverted for DVD widescreen on DVDA and HD-DVD on 3XDVD via Ulead.

Jeff

[Craig Irving]

Great post.


Thanks Steve.

[Steve Mullen]

Originally Posted by Jeff Kellam

Steve:

In a nutshell, does this mean editing HMC-150 footage in Sony Vegas Pro 8.0c will be problematic or impossible in the highest camera quality setting which I assume is a higher profile and bitrate?

Now that Vegas supports Canon, which uses HIGH profile, it "should" input from the 150. But, we have no idea if Pana is using pure AVCHD since it calls it's format AVCCAM.

Given Sony's past record, one could bet if AVCCAM requires any change -- Sony might not make the changes.


UPDATE: In my first post, I said "What all this means is Sony -- in keeping with it's public stance that AVCHD is a "consumer" format only cares about MAIN Profile at Level 4.0 -- which means a max data rate of 20Mbps. It need support HIGH Profile at Level 4.1 in VEGAS only if it chooses to."

Sony does export using HIGH. But they still limit the data rate to 16Mbps!

[Jeff Kellam]

Steve:

In the Panasonic white paper on AVCAM, the say that the Panasonic uses AVCHD, H.264, Mmpeg-4, level 10.

What is level 10?

Jeff

[Tom Roper]

I would assume that to be 4.1. If the profile is greater than 4.1 like 5 or 5.1 then it will not play on any blu-ray player, but it will play on the computer. The only solution is to re-encode the video to profile 4 or 4.1.

Vegas will not export higher than 16mbps but DVDA will export AVC up to 40mbps.

[Colin Barrett]

This is really useful info. I've just been playing with the new upcoming Canon HF S10 AVCHD camcorder (24Mbps) and having imported clips into Premiere Pro CS4 I've noticed just how difficult it is to manipulate the clips smoothly. By comparison, I've also been shooting stuff with a new Panasonic HDC-SD200 AVCHD (17Mbps) and I've had no such problems.

The above info probably explains why! :-)

I might now supplement my review, which can be seen here:

SimplyDV Review: Canon Legria HF S10 AVCHD Camcorder

Colin
(SimplyDV, UK)

[Steve Mullen]

Originally Posted by Colin Barrett

I might now supplement my review, which can be seen here:

SimplyDV Review: Canon Legria HF S10 AVCHD Camcorder

Colin
(SimplyDV, UK)

Hi Colin,

Where its performance suffers very slightly is in shots where there’s a steady, consistent movement -- such as a fairly fast tilt down a tree or a panning shot across a scene with lots of detail.

WHAT DOES THE VIDEO LOOK LIKE?

Whether or not this is due to the so-called rolling shutter effect or the high 24Mbps data rate is unclear, but the resulting effects were noticeable when imported into an Apple iMac and edited in Adobe Premiere Pro CS4 prior to outputting as a full HD specification file.

BUT YOU DIDN'T SEE THEM WHEN YOU PLAYED VIDEO ON THE CAMCORDER -- CORRECT?

These increased as clips using higher compression (lower quality settings) were used, though that’s hardly surprising.

THE *INCREASE* IS A CLUE THAT THESE ARE RELATED TO COMPRESSION

Interestingly, a similar sequence from Panasonic’s HDC-SD200 (17Mbps) didn’t display these characteristics, so perhaps that’s a clue.

IT LOOKS LIKE
the software codec Adobe is using is either

1) a poorly implemented 4.1 codec

2) a 4.0 codec trying to handle 4.1

3) not enough compute power for 4.1

Here's some more for folks to think about:

1) 4.1 allows the option of the encoder to use 4x4 macroblocks on areas with fine detail instead of being locked into 16x16 macroblocks. It takes far more computation to work with 4x4. But, it is an OPTION.

2) 4.0 can have only 1 B frame while 4.1 can have up to 4 or 5. It takes far more codec memory to work with more than 1 B frame. It is an OPTION.

So my guess is that when folks say a QUAD 2.66GHz computer is required to play AVCHD they may be talking about 4.0. It's likely that 4.1 CAN require much more power.

PS1: It's possible that although Canon used 4.1 Profile in the past, they didn't use the 4x4 option and/or the option to use more than 1 B frame. It all depends on the hardware encoder. Each generation uses more of the h.264 toolkit.

PS2: The GPU can be used to aid decoding. It's possible the Premiere codec doesn't use the GPU.

Bottom-line, for many situations -- given the lack of information consumers get -- the only option is to transcode AVCHD to something else. For example, I can get iMovie 08 to edit AVC, but editing performance is simply too poor to really be acceptable.