Faster! Faster!

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admin
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Faster! Faster!

Post by admin » Sun Jul 25, 2004 12:20 am

I've spent most of the past week optimising various parts of Cino:

* Increased efficiency of reading input stream
* Huffman decoding re-expressed in assembler.
* IDCT code tuned a bit further
* motion compensation routines speeded up (this is the biggy because the Iyonix has a fast CPU core but a relatively slow memory interface)
* optimised a bit more of the CPU-intensive core of AC3 decoding

So, there's no longer any need to play from RAM disc ;) It's playing at about 50% real-time (12.5fps) on average from HD, when all video & audio is decoded and rendered, which means that by dint of dropping B-type pictures DVDs are now comfortably watchable and the audio rarely breaks up.

I had a look at the profiling info playing from DVD and, with all the other stages being much faster, I'm now wasting about 25-30% of the CPU time just fetching the data from the disc (still PIO, you see)..... so, I guess it's about time that I got the DMA ATAPI stuff working & polished off! (That's why you have to play from HD at the moment to get good playback, not because the HD is intrinsically faster. In fact we only need to read about 2-3MB/s.)

Having done all this work tuning my MPEG decoder - on a processor that, frankly, was never intended for playing video :!: - we'll be looking for other uses. Suggestions on the back of a postcard, please :)

acorndave
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Joined: Fri Apr 09, 2004 6:25 pm

Faster, Faster

Post by acorndave » Mon Jul 26, 2004 1:05 pm

How about Video Capture ? (via Firewire maybe ?), so that I can download stuff off my Camcorder and burn it (author it) to DVD (assuming RISC OS gets some decent DVD burning ability that is)

That way I could get rid of my Windows PC altogether !

admin
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Re: Faster, Faster

Post by admin » Mon Jul 26, 2004 10:00 pm

acorndave wrote:How about Video Capture ?
That way I could get rid of my Windows PC altogether !

Well, I'm all for that! :)

The MPEG decoder could be useful for playing the video you've captured, but it's not really going to help get the video into your Iyonix or onto DVD.

Re DVD burning I understand it's being worked on already. I'm not keen on burning DVDs myself, but our DVDFS module may include support for DVD-RAM in a later release, fingers crossed.

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