Is AVCCAM the Emperor's New Codec?

[bcarson@bitstream.net]

I've been working with Panasonic cameras since my DVX100b days, a camera I really enjoyed using. Now I have an AF100, and I'm getting professionally unacceptable results. I've been doing a lot of reading about the AVCCAM codec, and it seems like 90%+ of people feel it's a wizardly codec, with wonderful detail and color. But then there's that 10% who claim the codec is weak and subject to unacceptable blockiness. Unacceptable blockiness has been my experience, too. If I'm doing something wrong, I hope one of you here can point it out to me. For starters, I've read Barry's book, and I've tried the Abel scene files. I black balance when I turn the camera on. I'm using a variety of Canon FD lenses, but this attached example is from a Lumix 14-140. The DRS is off. I see the blockiness if the gain is high or low. It's there regardless. I punched up the levels on this example to demonstrate a point, but even with the levels normal, it's there. This was shot 720PH, pulled into FCP 6 as ProRes422. I exported this frame into Photoshop and punched up the levels to make the point for those who might not see it otherwise. Here's the thing, I have a number of projects going and everything shot with Panasonic cameras by various people has this issue. Some of the footage looks OK, but if you try to grade the color, it falls apart. Some of the footage come from a Sony PDWF800, and it's breath taking. I can grade or work with Magic Bullet, and it all looks wonderful. Yes, it's a $33,000 camera. My question is, is this best the AVCCAM codec can do? Are the 90% crazy, or are the 10% doing something wrong? If so, what is it? I'm so very open to suggestions. Thanks! Bill

 

[Gary Huff]

Hey Bill, have you looked at the original footage at all? You mention a ProRes transcode, which is a step in the workflow chain that can fail, so I'd like to hear more about your work with the .MTS files on the card, not the transcodes.

Also, grading AVCHD is generally not a good idea for anything heavy duty. The codec is not built for that. It's 4:2:0 at 24Mbps for HD. The Sony cam is shooting XDCam 50Mbps 4:2:2, which is more ideal for grading. If you want that level of codec robustness from the AF-100, you should try to get footage with an attached PIX 240, Nanoflash, or Atomos Samurai external recorder. It's not ideal, but outside of the BMD Cinema Camera, you're not going to find a large sensor camera that shoots to anything other than AVCHD for less than $15,000.

 

[Hywel]

The dissatisfaction with the results of the on-board codec was a big part of why I upgraded to a Scarlet.

I believe people have better experiences shooting with external recorders, although this doesn't fix the 8-bit banding it does help with a lot of the other problems that make the footage turn to ugly mush the moment you start to grade.

Your example, though, looks spectacularly ugly even for the on-board codec. It looks over-sharpened, and I wonder if that grey chair with the greenish patches and ugly macroblocks was actually causing just a hint of moire or aliasing? I know the AF100 has an optical low pass filter to try to fix that, but fine cloth weave can still be problematic if you get it just at the wrong distance and in sharp focus, especially if you then do any sharpening to the image. I think that's more likely to be the issue here than the transcode to ProRes, which is usually fairly painless even though going from one lossless codec to another always risks worsening any artefacts.

Personally I've relegated the AF100 to a B-cam, if I'd stayed with it as my A-cam I'd definitely have wanted to invest in an external recorder. If I was buying now I'd definitely want to play with a BMD before buying anything else.

Cheers, Hywel.

 

[Bern Caughey]

Why capture in 720p? Have you tested 1080p?

I've never once shot 720p with the AF100, & wonder if it's optimal, or like the C300, introduces scaling issues.

 

[ZazaCast]

Focus might be a little soft in this frame (he was moving around), but I love the AF100. This is an untouched capture from the timeline (I edit natively in Vegas, .MTS files, 1080p).
Shot in a hotel room using natural light, a reflector and two clip-on worklights. The scene file is a tweak of my own. Works for me.... but I'm old school and try to achieve the look I'm going for in-camera so if there's any tweaking that has to be done, it's minor.

Sounds like the BMCC might be a better choice for you? :undecided

 

[dhart1949]

To my eye the scene looks over exposed. Also black level looks high. I tend to under expose (1/4-1/2 stop), particularly if there are harsh highlights when shooting with the AF-100 and gently tweak the exposure back up if needed in post. I doubt any codec will compensate for over exposure. Below is a still from an interview I shot with just two lights.

 

[PaPa]

Your image is wildly over exposed by a stop to two stops. Your scene is also not sufficiently lit to be able to see the detail where you're seeing blocks. Zaza hit his right on the money.

 

[bcarson@bitstream.net]

Naw, it's not over exposed; I bumped the levels up on the screen grab to highlight the purple blocks. I also try to underexpose if I can. ZazaCast, I see the same purple looking blocks in your screen grab, in the lettering. I also see them in your grab, dhart1949, although not as noticeable. I've continued to read and research all morning. I'm going to rent or borrow a NanoFlash when I get a chance, and see what I see. Right now I have the camera plugged via HDMI into a monitor, and while I'm not in love with what I see, those purple blocks are much harder to see... Yes, a $30,000 camera sure shoots a nice image!

 

[hscully]

Early on in the discussions of how to mitigate blocking suggestions included adding or allowing a little noise. In this grab from a recent shoot, I was worried that the walls in CUs might block so I used Cine D and let them fall under a bit. Additionally, I will in some cases here use the Neat Video plugin for premiere pro. It depends some on the deliverable. This is a narrative. Perhaps crisper commercial shoots won't allow for this adjustment.

One thing you don't have to sweat with the AF-100 is moire, for which I am consistently grateful!

 

[Lpowell]

I agree with Gary, once you've transcoded and altered the footage, it's no longer possible to be sure of the source of any problems you see. To draw any firm conclusions we'd need to see the original MTS footage, preferably downloaded from a sharing site.

However, the issues you're describing with discolored blotchiness in dark areas sound typical of 8-bit codecs like AVCCAM (aka AVCHD). The problem is not due to excessive compression, it's an inevitable result of the coarse quantization of dark shades at the bottom end of the 8-bit scale. In practice, this means that you cannot expect to get high-quality results when lifting dark details up out of the shadows in post.

If you want to be able to grade shadow details in AF100 footage, I'd recommend boosting the Master Pedestal setting to lift the dark shades into gray before they're converted to 8-bit AVCHD. You can then crush them down into black as far as you like in post. The drawback is that highlight headroom will be reduced, and you'll get blowouts in areas like the arm of the striped couch in your sample footage. Conversely, if you want to preserve highlight detail, you'll need to lower the Master Pedestal setting, giving you more highlight headroom along with crushed shadow detail.

In my experience, the AF100 produces its best results with low-contrast lighting. With harsh lighting, you can get either good shadow detail or decent highlights, but you can't have both at the same time.

 

[David Jimerson]

I've been working with Panasonic cameras since my DVX100b days, a camera I really enjoyed using. Now I have an AF100, and I'm getting professionally unacceptable results. I've been doing a lot of reading about the AVCCAM codec, and it seems like 90%+ of people feel it's a wizardly codec, with wonderful detail and color. But then there's that 10% who claim the codec is weak and subject to unacceptable blockiness. Unacceptable blockiness has been my experience, too. If I'm doing something wrong, I hope one of you here can point it out to me. For starters, I've read Barry's book, and I've tried the Abel scene files. I black balance when I turn the camera on. I'm using a variety of Canon FD lenses, but this attached example is from a Lumix 14-140. The DRS is off. I see the blockiness if the gain is high or low. It's there regardless. I punched up the levels on this example to demonstrate a point, but even with the levels normal, it's there. This was shot 720PH, pulled into FCP 6 as ProRes422. I exported this frame into Photoshop and punched up the levels to make the point for those who might not see it otherwise. Here's the thing, I have a number of projects going and everything shot with Panasonic cameras by various people has this issue. Some of the footage looks OK, but if you try to grade the color, it falls apart. Some of the footage come from a Sony PDWF800, and it's breath taking. I can grade or work with Magic Bullet, and it all looks wonderful. Yes, it's a $33,000 camera. My question is, is this best the AVCCAM codec can do? Are the 90% crazy, or are the 10% doing something wrong? If so, what is it? I'm so very open to suggestions. Thanks! Bill

View attachment 61282

I'm not really interested in defending AVCHD as a codec, because as an 8-bit, interframe 4:2:0 codec, there are always compromises. What I can tell you is that the AF100 is capable of creating images far, far, far superior to that one.

 

[Straw Man]

When I initially researched the camera, I found a wide range of quality in the images people produced with it. I ultimately decided to buy the AF100 because while the floor could be quite low, the ceiling for the camera was very high. It's been said in many other discussions and it's true: the AF100 is not a camera you can pick up out of the box, hit record, and get stunning images. You really have to learn how to tweak it and how to play towards its strengths while minimizing its weaknesses.

Here's a screen cap from a doc-style short film I recently completed: http://i.imgur.com/FAbS9.jpg

It isn't by any means "stunning," but I'm posting it as a counterexample showing what I believe to be a sharp, well-contrasted image. It's ungraded, avchd.

 

[dregenthal]

It's been said in many other discussions and it's true: the AF100 is not a camera you can pick up out of the box, hit record, and get stunning images. You really have to learn how to tweak it and how to play towards its strengths while minimizing its weaknesses.avchd.

Amen.