macarelo
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Re: Confused about GPU

Fri Nov 11, 2011 6:38 pm

I\'ve read all about the VideoCore IV, and how it is a very capable GPU, but then I also read that it may not be fully implemented in the OS.

My question is, will we have drivers that take full advantage of the GPU? Will we have H264 hardware acceleration on decoding/enconding? OpenGL?
Will I be able to watch cuevana.tv?

jamesh
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Re: Confused about GPU

Fri Nov 11, 2011 7:06 pm

OpenGL ES 2, OpenVG are definitely ready to go. With regards to H264 playback we will for the launch be providing a full media player that will play whichever codecs are included. I think there will be some OpenMAX stuff as well, but that is a right royal PITA to use, which is why the media player will be there. Encode is a bit more difficult to present without an onboard camera, and we havent said whether that will be available at launch yet. (AFAIK).

There are lots of threads on this subject in the forum. With taking a look.
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macarelo
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Re: Confused about GPU

Fri Nov 11, 2011 7:28 pm

Thanks Jamesh!

I\'ve been reading every thread I could find on the GPU, that\'s why I was a bit confused. I remember reading somewhere (can\'t remember where though) that the Quake 3 demo wasn\'t as fast as it could be because of drivers, and many posts like that led me to start this one.

What about the flash thing? Flash is not supported but we\'ll be able to watch youtube, I\'ve read. Isn\'t youtube flash-based?

AlanCox
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Re: Confused about GPU

Fri Nov 11, 2011 7:41 pm

Youtube also supports standards based video (Vorbis,H.264)

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mkopack
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Re: Confused about GPU

Mon Nov 14, 2011 4:04 pm

[quote]Quote from AlanCox on November 11, 2011, 19:41
Youtube also supports standards based video (Vorbis,H.264)
[/quote]

Right... When you hit the web site, it detects if you have the flash plugin installed. If you do, it delivers video over flash. If you don\'t, it uses one of the other video formats.

macarelo
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Re: Confused about GPU

Mon Nov 14, 2011 4:06 pm

Cool. I hope cuevana.tv works on the RasPi

jamesh
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Re: Confused about GPU

Mon Nov 14, 2011 5:03 pm

[quote]Quote from macarelo on November 11, 2011, 19:28
Thanks Jamesh!

I\'ve been reading every thread I could find on the GPU, that\'s why I was a bit confused. I remember reading somewhere (can\'t remember where though) that the Quake 3 demo wasn\'t as fast as it could be because of drivers, and many posts like that led me to start this one.

What about the flash thing? Flash is not supported but we\'ll be able to watch youtube, I\'ve read. Isn\'t youtube flash-based?[/quote]

The Quake demo wasn\'t quite as fast as we expected it to be - only about 25 instead of 30fps. (since we know the GPU standalone can do 30). Not sure whether that has been fixed yet.

As to Flash video, that won\'t work. And I\'m also not sure about other streamed video in webpages, as I haven\'t tried it yet.
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Re: Confused about GPU

Wed Dec 21, 2011 9:41 pm

Confused *2:
Is it possible to bring up the GPU, and have graphics output (even if just something like a simple frame buffer) with out an OS? Does the GPU binary used as a loader provide some form of OS independent API?
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Re: Confused about GPU

Thu Dec 22, 2011 3:42 am

[quote]Quote from DavidS on December 21, 2011, 21:41
Confused *2:
Is it possible to bring up the GPU, and have graphics output (even if just something like a simple frame buffer) with out an OS? Does the GPU binary used as a loader provide some form of OS independent API?[/quote]

There has to be some type of OS there, the SOC needs to take commands from something. You may see a very minimalist OS at some point that does exactly what you are stating without the bloat of a full featured installation. No matter how much you strip from something, it will still need to have functions to load various drivers, take input, and load media.

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Re: Confused about GPU

Thu Dec 22, 2011 4:06 am

I would argue that. Perhaps you are just being overly pedantic, but many applications of embedded systems do not use what would traditionally be considered an OS. Being just like any other CPU, this one operates on a simple principle - fetch instructions from RAM and execute them, and that does not require an OS, just a suitable list of instructions to execute (aka. a program). You don\'t need drivers, you manipulate the hardware directly, and handle input directly in the interrupts (or buffer it for your main loop).

RPi is a large enough device that to really get the best out of it and use all of its features well will require an OS, but it\'s not at all required to make it do something.

Obviously this is only suitable for relatively simple applications, and requires relatively extensive hardware documentation, but it\'s quite feasible. RPi might be bigger, but it\'s really not fundamentally any different than an AVR or 8051 that are more typically used in this way.

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Re: Confused about GPU

Thu Dec 22, 2011 5:52 am

Some would indeed say that any application running on bare hardware is its own OS, I am not one of these. Though my purpose for asking is OS development.

I would still like to know:
Does the GPU binary export any well documented APIs without using a user space library on an OS. That is to say something that can be easily accessed by way of an application that is running on bare hardware.
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Jessie
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Re: Confused about GPU

Thu Dec 22, 2011 6:02 am

Here read this thread...http://www.raspberrypi.org/forum?mingle ... pic&t=1581
From the sounds of it the first thing on the SD card is loaded. So if you want to make a custom OS in whatever programming language it will just load that. If a barebones single function device is what you want then it shouldn\'t be any problem for someone with some programming skills to make that and drop it on the card.

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Re: Confused about GPU

Thu Dec 22, 2011 6:36 am

Jessie:
I know that and have read that thread, my question is in being able to use the GPU. I would like to be able to do video output, and 3D acceleration functions would be very nice (more for math than graphics).
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Re: Confused about GPU

Thu Dec 22, 2011 10:41 am

[quote]Quote from DavidS on December 21, 2011, 21:41
Confused *2:
Is it possible to bring up the GPU, and have graphics output (even if just something like a simple frame buffer) with out an OS? Does the GPU binary used as a loader provide some form of OS independent API?[/quote]

Yes. The GPU boots Linux from a compressed file on the SD card. That file is usually the Linux OS, but could be anything.
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Re: Confused about GPU

Thu Dec 22, 2011 5:52 pm

Ok where do I find the documentation for this??????
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Re: Confused about GPU

Thu Dec 22, 2011 6:49 pm

Be patient young Jedi! The board isn\'t even released. I\'ve yet to meet the company that released the operating instructions on a product that wasn\'t on the market yet! ;)

Edit: yes I know that you\'re asking for documentation for a chip that does exist, but you\'re asking for it from a product using that chip, ergo you must be patient for the product to be in production to get what documentation they\'ll legally be allowed to release.
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Re: Confused about GPU

Thu Dec 22, 2011 7:29 pm

It makes it difficult to develop an operating system that relies heavily on video output if you do not know how to do video output.

I will wait.
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lyzby
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Re: Confused about GPU

Thu Dec 22, 2011 7:44 pm

>Obviously this is only suitable for relatively simple applications
On the contrary, I would say that writing to the bare hardware is suitable only for extraordinarily complex and time-sensitive applications. For anything less that that, you just plug in your favorite OS on an SD card, apply power, and program in your favorite package-installable programming or scripting language, using the available API.

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Re: Confused about GPU

Thu Dec 22, 2011 8:33 pm

[quote]Quote from DavidS on December 22, 2011, 19:29
It makes it difficult to develop an operating system that relies heavily on video output if you do not know how to do video output.

I will wait.[/quote]

By the time the OS kernel is started the video is already up and running so you can get a display of the boot sequence. I\'m not sure how you talk to it though. Sure it will be documented at some point - but it isn\'t at the moment as far as I know.
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Re: Confused about GPU

Fri Dec 23, 2011 9:57 am

How mach GPU take RAM from main 256 RAM, when working in OS? (64)

jamesh
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Re: Confused about GPU

Fri Dec 23, 2011 10:49 am

You can specify the amount of RAM allocated to the GPU, not sure that the minimum is need for the framebuffer, but if you are using the camera the GPU needs more for the camera buffering.
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Re: Confused about GPU

Fri Dec 23, 2011 12:00 pm

[quote]Quote from AlanCox on November 11, 2011, 19:41
Youtube also supports standards based video (Vorbis,H.264)
[/quote]

Youtube supports h.264/WebM if you enable HTML5 video at www.youtube.com/html5

Hopefully raspi guys will test 1080p flash, 1080p webm and 1080p h.264 and report back.

Will there be any way to hardware decode 1080p .mkv files using vlc player in the future or will users have to use your player?

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