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Sabtu, 10 September 2011

3-D HDMI 1.4 PS3



How and why the 3-D HDMI 1.4 update is possible for the PS3

HDMI 1.3 and HDMI 1.4 use the same plug but the latter has two more wires connected.  HDMI 1.4 also uses high speed certified cable.  Besides the Ethernet and audio return lines, the only non-hardware differences are handshaking routines, 3-D support, extended color palette and 4kX2K resolution support all of which in the PS3 can be implemented by a software update

The bandwidth (transfer speed) of 1.3 and 1.4 HDMI ports is the same.  Hdmi 1.3 cable comes in standard and High speed.  At lengths of less than 3 feet, the bandwidth should be the same. 

  • Standard  (category 1) is the equivalent of a 720p/1080i signal.
  • High Speed HDMI cables can handle 1080p signals at increased color depths, higher refresh rates and resolutions.


HDMI 1.4 requires 3-D resolution support: 1080P@24Hz and 720P@60Hz  other modes and frame packing methods may be supported but are not required.  The HDMI 1.4a addendum adds required support for 2 more 3-D framepacking modes (1/2 resolution) for set top boxes and also lists all older 3-D ready display techniques.  

HDMI 1.4 and 1.4a when used together provide handshaking routines to support ALL existing 3-D ready displays. Updates to firmware for the 3-D ready TVs may be possible so that they automatically handshake with a 1.4 source to negotiate a common display format (if supported). (Some of the 3-D ready displays do not support framepacking and from statements by Sony employees, display agnostic was a feature stressed which means SONY will not support those.)

The PS3 appears to have an automatic-manual setting (picture leaked) for this 3-D HDMI 1.4 negotiation with Manual requiring the PS3 to be set to a 3-D output mode like DLP checkerboard for a non-upgraded firmware DLP 3-D ready HDMI 1.3 TV.  (Sony may support DLP checkerboard, Panasonic and Samsung blu-ray players do.)


For a device to be rated as HDMI 1.4 requires it support a framepacked (two frames and meta data)  1080P and 720P signal.  The TV takes the two frames and displays them at 120Hz (or faster) so with framepacking from the source you have two sequential frames in the time it takes for one 60Hz frame.  The shutter glasses alternate turning (on-off) (off-on) at this rate (120Hz).  This results in very little flicker and with good glasses almost no reduction in brightness or contrast.  The framepacking method can vary. A device can support some of the HDMI 1.4 required standards but can not call itself compliant.  


Framepacked= two 3D (both eyes views) frames are packed into the timing window of 1 2-D frame (24-60Hz). There are multiple methods to pack these two frames into this timing window (there are only 4 required methods for certification).  Framepacking allows flexibility in method as well as allowing the display after unpacking these frames to display at any rate it chooses as plasma, LCD and DLP have different optimum refresh rates. 

Framepacking allows the HDMI 1.4 3-D information to be display agnostic and the same source information as provided by the PS3 can be used with any display engine (LCD 240Hz, DLP120Hz, Plasma 640Hz, OLED 120Hz) and with any technique for displaying 3-D (Autostereoscopic, Field sequential Shutter, field sequential polorized, dual display polarized or with any new technology developed in the future).

The output from the 1.4 source device (PS3 for instance) is 60HZ or less not 120Hz.  Without support for 3-D built in to the display, no HDMI 1.4 3-D mode, required or optional, will work.  The fact that a TV has a refresh rate of 120Hz does not enable 3-D support. A half resolution side by side mode can be viewed in 3-D by crossing your eyes or with a cheap hand held mirror assembly.  Youtube has been experimenting with this.

The HDMI 1.4 source device outputs a 60Hz or less video signal.  When 3-D is active the framebuffer in the PS3 doubles in size and two frames are packed into, (timing) at double the transfer rate, the timing window that represents the 60-24 Hz frame rate associated with TV.   The HDMI 1.4 TV recognizes this and pulls the two frames out of this "window" and displays the two frames alternately at 120Hz resulting in two 60 HZ (right and left) images for 3-D appearing to occur simultaneously because of persistence in the eye.  The double 1080P resolution also supported by HDMI 1.4 is possible because the frame buffers in a HDMI 1.4 device have to be twice as large for 3-D so why not make these buffers available for double res if you are not doing 3-D. 


1) The XBOX can not do 1080P 3-D at 60Hz due to the 1.2 HDMI ports transfer speed limits but the HDMI 1.2 port may be able to do 1080P 3-D at 24Hz. 

2) The Xbox hardware GPU advantage over the PS3 RSX is lost when doing 1080P 2-D and 720P 3-D.  The PS3 then becomes, by contrast,  more efficent and easier to program and every bit counts when two frames must be generated in the same time.  This was the reason  the PS3 has a configurable frame buffer and some of the graphics processors in the Nvidia 7800 were removed in favor of the CELL SPEs. 

How did the Xbox do the 3-D games Avatar and Gen Tao.  Those were done half resolution 720P. Another interesting point is that the game Avatar rendered at 30Hz on both the Xbox and PS3 but packed (two frames at half resolution) into, depending on display device, 60 Hz frames.  My DLP required 60HZ checkerboard  (slightly more than half resolution) double frame (packed) and the DLP pulled the two frames out and displayed at 120 Hz. 

Many were questioning the PS3 ability to do 3-D as the assumption was the PS3 was less powerful due to comparisons in frame rate between Avatar 3-D running on the Xbox and PS3.  The difference here is SONY did not provide 3-D SDKs for Avatar but is now providing the SDK calls for 3-D and developers will now have proven code to write 3-D games. MS may do the same at some point. 

The XBOX half resolution 3-D will be enough for the streaming 3-D being proposed for current set top boxes (HDMI 1.4a addendum).  Some of the proposed standards for HDMI 1.4 will probably be supported by the XBOX.  The PS3 can support all  HDMI 1.4 display modes, some of which are NOT possible for the XBOX due to the HDMI 1.2 port.

The PS3 RSX uses the 256 meg of Gddr3 shared memory for video buffers.  The Xbox uses 10 Meg of very fast video ram INSIDE the xbox GPU for a buffer.  This makes it easier for the xbox to do things like AA but makes it less flexible.  The design criteria of the Xbox was for a very efficient 720P game machine.  The PS3 was designed to be more flexible and for this flexibility the PS3 takes a hit in efficiency at lower res.  But it allows software configuration for things like new video modes including 3-D and double 1080P res. 

Each of the 6 Cell SPE processors is faster/more efficient at video processing than each of the Power PC processors in the Xbox.  You have to think of them as idiot savants, faster at repetative tasks.  This makes the Cell faster where it counts and the choice of memory that is 2 times faster than the XBOX GDDR3 supports the faster speed necessary for 1080P and 3-D on the PS3.   (As idiot savants the Cell SPEs require more supervision and more complex code; this is the reason many developers were not getting the most out of the PS3).

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