[gibsonlp]

Hi,
I thought about modding an apple TV, but before I even start - I couldn't find anywhere where it says it actually works well with high bitrate files.

I have no problem with opening the box and putting in the decoding card, I also don't mind (and actually prefer) to install linux on it if it helps with the performance - but before I even start working on it - is it something I should expect from this hardware combination?

True, most of the files I play on it are ~9mbit but I would like to be able to play "heavier" movies as well if the need arises.

So, what do you say?

Thanks.

[dan1son]

Supposedly the BCM970015 is better than the 970012 in regards to high bitrate files. My setup can play high bitrate H.264 files just fine, but still struggles with VC-1 files. I'm running ubuntu 9.10 on my ATV with the old layout BCM970012 card.

Both cards will struggle with files that have an excessive number of reference frames, but if you're talking about blu-ray rips without modifications you should be good to go.

If you already have an ATV, the CrystalHD card is a great add-on making it far more useful. If you don't already have one, you might consider an ION based box of some kind.

[gibsonlp]

Thank you for your reply.

I don't already have an apple TV, I simply like modding equipment and I really like the Apple TV's look.
I know that an ion solution is probably more suitable and in fact - that's the solution i've been "pushing" to my friends whenever one looks for a media center without a large storage on it.

As for the reference frames - would it handle an excessive amount of reference frames in a "standard" h264 bitrate? (say - around 10mbit)

Thanks again.

[defiler]

As for the reference frames - would it handle an excessive amount of reference frames in a "standard" h264 bitrate? (say - around 10mbit)

As I understand it, the reference frames are ramped up beyond spec to try to push the image quality up. You're not going to do that on a 10Mb feed because it wastes bandwidth, and you've already chosen to sacricide the quality by dropping the bitrate that low.

The CrystalHD card does all the decoding, and it's built to the BluRay movie spec. If your video is within spec it should be able to decode it. I find that it's the memory constraints in the ATV that cause more trouble. Of course, with the ION, I believe the decoder is in software with assistance from the chipset so it can be designed to cope with these out-of-spec formats.

Two things. One - I can play the BluRay rip of Star Trek and it generally nails it. That's a 40Mb disc. There are a few artefacts in one scene that I can remember, but that was an old version of XBMC - I've not checked it for a while. There were a few dropped frames due to the memory, but nothing I'm going to cry into my cornflakes over.

Two - if you're ripping to a .mkv file you'd generally find it worthwhile to drop the surplus soundtracks and subtitles. Star Trek drops from 40Mb/sec almost to 30 just by doing that. Aiming to handle 40Mb/sec is maybe a bit extravagant.

[dan1son]

Reference frames simply make the compression more efficient. So you usually get higher quality with a smaller file size, but it requires more memory and effort to encode and decode.

The reference frame memory requirement is unrelated to the bitrate. If you have a file with 10 reference frames, the decoder has to have 10 1920x1080 (24-bit color depth) raw images in RAM. That's 1920*1080*24 * 10 = 497 664 000, almost 500 megs. The 970012 and 970015 both have 512 megs, hence the 10 reference frame upper limit.

As defiler mentioned, the card is built around the blu-ray spec. The BCM970015 goes just a hair past it (supporting L4.2 profiles on H.264 1080p files, where blu-ray stops at L4.1). Any Blu-Ray rip "should" play fine...

The max bitrate of 40mb/sec on the CrystalHD cards is only the video feed. It doesn't touch the audio. The Max bitrate for blu-ray video streams is 40mb/s so it still fits in there. You'll find most discs are still below that spec. Also keep in mind that's the "upper limit." Since L4.1 used by blu-ray is a variable bitrate encode, you'll see the average is considerably lower than 40 even if the file touches it once or twice.


And actually VDPAU does more of the work in the GPU than the CrystalHD. CrystalHD has to pump the video stream into the CrystalHD, then pull the decoded uncompressed stream out, do some work on it, and pump it into the video card for output. VDPAU just pushes the stream to the GPU (which can decode and display it without the memory bus or cpu seeing it again). The only reason ION can handle higher specs than the CrystalHD card is because it can have more memory and it has more processing power for decoding. Simple as that.

The CrystalHD was just designed for hardware video decoding, where the IONs were designed for gaming as well so they have more overhead.