[iksis]

I have noticed this issue on several files I have played recently. It seems to only happen in XBMC on my Mac. The picture will suddenly appear fuzzy for a while and then return to normal. I have tried running the same files on XBMC for windows and also ran the files on my Mac through VLC - both of these resulted in no problems.

I have found the problem in a few (but not all so far) mkv container files. x264 codec.

The problem is a bit difficult to describe so I have included a couple of screenshots of it happening.
http://i.imgur.com/rrUEO.png
http://i.imgur.com/h0CFb.jpg

Log is also included:
http://pastebin.com/KnDiPgbw

OSX 10.7.2
Macbook Pro 2011
2GHz Intel Core i7
4GB 1333 MHz DDR3
AMD Radeon HD 6490M 256MB

Thanks for your help.

[davilla]

That's called 'macro blocking', it's when the decoder fails to decode properly. It's typically due to non-standard encoding methods like choosing a greater number of reference frames for a given profile/level.

Why are non-standard encoding methods used ? To reduce the size of the encoded content. Also known as 'smashing'. FFmpeg is quite tolerant to non-standard encoding methods while hardware decoders (such as VDA) in general are designed and programmed to handle standard encoding methods. There's a reason why such 'specs' exist and this points out those reasons.

The only thing you can do is turn off VDA. Once you do this, then be prepared for much, much higher CPU usage as ffmpeg will be used to software decode the content.

The nvidia GPU based Apple products seem to handle these much better than the intel/ati GPUs.

[iksis]

Ah I see. That's great, thanks for taking a look.

Cheers.