dom
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5572
Joined: Wed Aug 17, 2011 7:41 pm
Location: Cambridge

Re: New blog post from JamesH on the main page

Wed Feb 01, 2012 9:43 pm

You can work out the cost of each audio/video codec here:

http://www.streamcrest.com/Lic.....ator9.html

Nexy
Posts: 73
Joined: Sun Oct 09, 2011 9:03 pm

Re: New blog post from JamesH on the main page

Wed Feb 01, 2012 9:57 pm

Is CPU decoding SD MPEG2 really that resource hungry that it can't be done on the CPU? The FAQ says "Overall real world performance is something like a 300MHz Pentium 2, only with much, much swankier graphics." Not sure if my old AMD K6-2 350MHz was able to do it, but my 750MHz Althon sure was. Does the 700MHz RasPi fall closer to the former than the latter in it's ability to software decode codecs like that? I do appreciate that I'm literally not comparing apples with apples when it comes to "performance" in relation to clockspeed.

Somewhere (possibly in the blog comments, not that I can find it now?) it was mentioned it is possible to offload some maths to the GPU in a more general way using GPGPU, is that likely to be an option to accelerate the "software" decoding of MPEG2? I'd cite the comment but I'm seemingly utterly incapable of retracing my steps to find it.

WereCatf
Posts: 89
Joined: Thu Jan 26, 2012 7:16 am
Contact: Website

Re: New blog post from JamesH on the main page

Wed Feb 01, 2012 10:45 pm

Nexy said:


Not sure if my old AMD K6-2 350MHz was able to do it, but my 750MHz Althon sure was. Does the 700MHz RasPi fall closer to the former than the latter in it's ability to software decode codecs like that?


It falls closer to the former than the latter. And well, I do not know how well it could decode SD-resolution MPEG2, but as many people wish to use it as a mediaplayer it simply is out of question as DVD > SD and DVB > SD.

error404
Posts: 351
Joined: Wed Dec 21, 2011 11:49 pm

Re: New blog post from JamesH on the main page

Wed Feb 01, 2012 11:14 pm

It's hard to directly equate performance between different architectures with completely different design goals like that - but I'd be optimistic about software MPEG2 at DVD resolutions and bitrates. I remember doing it without much difficulty on a Celeron 400MHz back in the day, and as it's all integer math, the ARM should perform fairly well. No NEON though and that might be just the hammer to the kneecap that kills it.

Hard to say without having the device to play with.

onereader
Posts: 1
Joined: Thu Feb 02, 2012 12:20 am

Re: New blog post from JamesH on the main page

Thu Feb 02, 2012 8:38 am

WereCatf said:


Nexy said:


Not sure if my old AMD K6-2 350MHz was able to do it, but my 750MHz Althon sure was. Does the 700MHz RasPi fall closer to the former than the latter in it's ability to software decode codecs like that?


It falls closer to the former than the latter. And well, I do not know how well it could decode SD-resolution MPEG2, but as many people wish to use it as a mediaplayer it simply is out of question as DVD > SD and DVB > SD.



SD means 576i or 480i, DVD is limited to MPEG-2 720/704x576, that is SD, DVB-T can broadcast either 1080p H.264 (not common yet) or usually 720/704x576 MPEG-2.

The only difference is the bitrate, DVDs usually is up to 8Mbit/s while DVB-T has usually a lower bitrate according to how many channels there are in the mux. So you can assume that DVB=DVD=SD.

MerlinElMago
Posts: 3
Joined: Thu Dec 29, 2011 8:37 pm

Re: New blog post from JamesH on the main page

Fri Feb 03, 2012 8:44 pm

Hello Guys,

I've read the XBMC announcement with great excitement. Having read this thread, and knowing about the licensing issues, and not being disappointed at all by the device... I still want to express my interest at least in a MPEG2 codec. I say again: express my interest! (Just in case anybody is telling me to go and read the thread again). I would really appreciate if the Foundation could stay on top of that matter.

I for myself will buy a few anyway, with or without MPEG2 support. But it would just be a hammer to see an XBMC Media Center being able to receive a MPEG2 DVB-T Stream sent from my VDR (Video Disc Recorder).

I could of course argue as well that, being thought for young people to learn programming, it will surely attract more "baby"-programmers the more multimedia capabilities this device has.

So please team, keep at it!

Best Regards

Merlin

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Chromatix
Posts: 430
Joined: Mon Jan 02, 2012 7:00 pm
Location: Helsinki

Re: New blog post from JamesH on the main page

Fri Feb 03, 2012 9:07 pm

Software video decoding at SD is at least theoretically possible.  While the ARM11 core doesn't have NEON to call on, it does have a narrower form of SIMD, operating within the 32-bit GPRs, which seems to be aimed at video.  It's not going to be easy though.
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