[vlc] Re: OS X 10.4 (Tiger), CoreVideo and HDTV...

[Eric Petit]

On Mar 7, 2005, at 23:34, Matthew Neilson wrote:
> For starters, is there any truth to the rumor that, if implemented in 
> a player such as VLC, CoreVideo may allow for seamless playback of 
> 1080i (60fps) high-definition transport streams on the current line-up 
> of Powerbooks? As far as I am aware, no one has observed 'perfect' 
> playback of 1080i *.ts files on a G4-based Mac. However, if I'm 
> understanding things correctly, CoreVideo will allow for the massive 
> amount of (currently untapped) power in the GPU to be used to its full 
> capacity, therefore giving older machines a new lease of life in the 
> video-playing stakes. Correct?
> Now, taking this a little bit further, my 1GHz TiBook (ATI Mobility 
> Radeon 9000, 64MB DDR) can *almost* play 1080i transport streams using 
> VLC 0.7.2 - it's watch-able, but there clearly a quite a few dropped 
> frames. In theory, could my graphics card give the extra push that is 
> needed for seamless playback?

  There are two main CPU-consuming tasks when playing a HD stream: MPEG 
decoding and video display.

  It is unlikely we can make MPEG decoding faster. Hardware-accelerated 
decoding does exist (especially with ATI cards) but no one has had 
enough documentation and/or time to complete an opensource solution. I 
believe that if it had to be done some day, it would have be done by 
now - CoreVideo isn't going to change anything about it.

  Display is about colorspace conversion and scaling. 0.7.2 already does 
quite a good job about this, since it only performs a simple YUVP->YUY2 
conversion and let the GPU handle the scaling and the YUY2->RGB 
conversion for display. I don't know much about what CoreVideo can do 
(and I can't find anything about it, I guess only people who purchased 
the Tiger Early Start Kit do), but the only hope I can see is that it 
may directly handle YUVP in hardware. *If* it does, it might give the 
"extra push". From what I have seen, the CPU utilization when reading a 
MPEG-2 stream is currently about 75% for decoding and 25% for display.

> Also, is it at all likely for developers of the OS X port to include 
> support for CoreVideo in future versions of VLC? Of course, it's 
> clearly something that would have to be specific to the OS X port, and 
> I haven't the slightest idea as to how easy or difficult a task it 
> would be for someone to implement this, but is it something you might 
> look into?

  Platform-specific features aren't unusual in VLC, as long as there's 
an interest. As I said, we can't look into it until we have the dev kit 
in our hands.

> Finally, would a feature such as this be difficult to include without 
> causing problems for people running VLC on pre-Tiger versions of OS X? 
> Or could it be a hidden preference (such as the glorious OpenGL 
> semi-transparent/rotating cube effect) which requires finding and 
> turning on?

  I assume it is possible to perform some Tiger detection and behave 
different ways depending on the system, just like we check for 
QuartzExtreme now in order to enable or disable OpenGL drawing.

-- 
Eric Petit <titer at m0k.org>

-- 
This is the vlc mailing-list, see http://www.videolan.org/vlc/
To unsubscribe, please read http://www.videolan.org/support/lists.html