Why can my PPC play DVD's fine, but not the same file in .mp4?

[MrPilot]

What about the DVD decoder card for the Wallstreet and Lombard G3's?

for mp4's? dvd decoder isn't the OP's question. But a valid point.

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Using OpenGL to render video is still a form of acceleration, disable it on OS X and see how your Mac "feels" & Quicktime playback suffers like an iMac 233-333 non-supported Rage II/Pro
Bitrate matters, however the encoder is a factor--some MP4s are pure H.264 but others may use MPEG(some YouTube MP4s have their video compressed by MPEG and audio track is MP4)
You have "hardware acceleration" on ATI Radeon 9xxx series, ATI optimized the platform as it was part of their "All-In-Wonder" platform--MacOS drivers take advantage of the OpenGL strength(which nVidia lagged until the 6-series). Try comparing video playback on a 12" vs 15" PowerBook to an external monitor, a slower 15" will spank a higher clocked 12"... my 12"(1.33ghz) chokes on 720p EyeTV recordings however a slower 15"(1.25Ghz) is smooth even though it has a 4200 RPM HDD.

nVidia Pure Video H.264 acceleration launched on the 6-series... which is why the 6600GT is popular for Power Mac G5 owners

you are mixing 2d/3d graphics acceleration (opengl: screen drawing, shaders in games etc) with video decoding (VDADecoder)... two different things. Be reminded that this topic is about using the gpu to assist the video decoding process and it's not about hardware acceleration in general... Unfortunately opengl does not help with the decoding process, meaning ppc users are stuck with altivec only

 

[MrPilot]

While some GPU's in PowerPC Macs have hardware MPEG4 or h.264 decoding abilities, it isn't used in PowerPC Mac OS X. Support for such things didn't come around until 10.6.3, and even then only with some of the then newer GPUs.

I wish apple would have released vdadecoder for such cards Specially considering all the cards used in the later generations of the ppc's I've used have that capability.

 

[happyfrappy]

you are mixing 2d/3d graphics acceleration (opengl: screen drawing, shaders in games etc) with video decoding (VDADecoder)... two different things. Be reminded that this topic is about using the gpu to assist the video decoding process and it's not about hardware acceleration in general... Unfortunately opengl does not help with the decoding process, meaning ppc users are stuck with altivec only

I'm only going by the developer data which Apple published...
Apple Developer Notes lists this for the 15"/17" PB G4 2003(nVidia 5200 doesn't list any form of acceleration):
The features of the Mobility Radeon 9600 include
● graphics processor clock speed of 303 MHz
● memory clock speed of 203 MHz
● support for 64 MB of DDR video memory with 128-bit interface
● 2D and 3D graphics acceleration
● video acceleration
● support for MPEG decoding


Still doesn't explain why there is a MP4 playback gap between nVidia 5200 vs Radeon Mobility 9600/9700 for video playback on a similar external monitor(1680x1050) when there is just a minor speed difference between machines. If everything is altivec, a 12" 1.33Ghz(2004) should handle MP4s similar to a 2003 17" PBG4. AFAIK, 2003(FW800) 15" 1.25Ghz processor is from the same family as the 1.33Ghz used in the 17" and the 2004 revision. Radeon 9700 speed bump used a newer chip revision where the 1.5Ghz had a pipeline adjustment.

 

[MrPilot]

I'm only going by the developer data which Apple published...
Apple Developer Notes lists this for the 15"/17" PB G4 2003(nVidia 5200 doesn't list any form of acceleration):
The features of the Mobility Radeon 9600 include
● graphics processor clock speed of 303 MHz
● memory clock speed of 203 MHz
● support for 64 MB of DDR video memory with 128-bit interface
● 2D and 3D graphics acceleration
● video acceleration
● support for MPEG decoding


Still doesn't explain why there is a MP4 playback gap between nVidia 5200 vs Radeon Mobility 9600/9700 for video playback on a similar external monitor(1680x1050) when there is just a minor speed difference between machines. If everything is altivec, a 12" 1.33Ghz(2004) should handle MP4s similar to a 2003 17" PBG4. AFAIK, 2003(FW800) 15" 1.25Ghz processor is from the same family as the 1.33Ghz used in the 17" and the 2004 revision. Radeon 9700 speed bump used a newer chip revision where the 1.5Ghz had a pipeline adjustment.

There are many reasons as to why video playback would suffer between similar models. The OSX UI can be offloaded from the CPU to OpenGL on some gfx cards thus leaving the CPU with more available cycles for video decoding. I have tried down-clocking the ATI mobility 9700 to only 5% of original speed and noticed no change in video playback performance even comparing it to over-clocking

Also memory and cache-type can give a huge boost to general performance.

And lastly, yes altough apple provided some macs with graphics cards with video acceleration, they have for some obscured reason decided not to implement that into OSX 10.5.8 PPC

to use video acceleration you'd need three things:
1) Update OSX to include API's for video accel. like VDADecoder on Intel macs
2) Compile the API itself
3) Update software to use these API's (like VLC, XBMC, Quicktime Player, Flash etc)