Curiosity about reproduction speed and resizing

[PaulJBis]

Hi all:

First post here :-). I have here a DivX 5.03 clip that I needed to use in a video editing project, and since editing with interframe compression codecs like DivX can be a pain, I converted it to both MJPEG (PICVideo codec) and HuffyUV (to test which one would take less space, etc.). While doing so, I noticed something interesting:

-When using Windows Media Player 6.4 to play the MJPEG and HuffyUV clips, the CPU usage goes up to 100% when playing at 200% zoom, and the movement is noticeably jittery. When playing at a normal size (100%), the CPU usage goes down to 50% or so and it plays the clip without problems (I have a Duron 800Mhz, BTW).

-With the DivX clip, however, the CPU usage never goes beyond 35%, and what's more, it never goes up, even when changing resolutions. No matter if you play it at 100% or 200%, the CPU usage stays the same.

Why is this? I can understand that the other codecs are more CPU-intensive than DivX, but if playing a clip at 200% resolution takes more CPU resources, it should do so regardless of the codec used, shouldn't it? Is there something "special" about DivX that makes it effortless to resize the clip?

(Note that this isn't a problem or a request for help; I'm just asking because I'm curious about it).

[Wolfman]

I think the problem lies not in the intensity of the codec as divx files are more heavily compressed and therefore more cpu intensive to decode, But I would think that it is your video card that is having the problem and cannot shuffle the memory around fast enough.. are you using a) a laptop (ergo low qual gfx) b) a puny graphics card C) a machine with small memory (128mb).. or all three... what IS your machine spec?:D


size DOES matter!

[PaulJBis]

I have 256 Mb. of RAM (and a Duron 800Mhz, as mentioned), and my video card is a GeForce4 MX420 with 64Mb (a puny one by today's standards, I understand :-), but I thought it would be enough for something as simple as playing video files).

Anyway, I understand that DivX clips are more compressed and should be more CPU-intensive, but my experience is that CPU usage is actually lower when playing DivX than playing MJPEG or HuffyUV files.

[Wolfman]

Not actually all that puny .. certainly good enough for playback (I have mx460 64mb) .. it must be the codecs you have installed.. I thought you might have integrated motherboard gfx (shared ram (shiver)).

[DigitAl56K]

Its likely to be that the HuffYUV clip isn't using your graphics card video overlay.

Things to check:
Do you have DirectX9b installed?
Do you have the latest drivers for your graphics card installed?
Have you reduced the hardware acceleration slider in the "Troubleshoot" section of the Display Properties control panel (under settings/advanced)?

[PaulJBis]

Okay, things to check...:

* I have Windows 2000 SP1 (because I also use Avid XpressDV, and it "is not supported for SP3 or 4").
* I think my version of DirectX is 8.1, but I'm not completely sure (!).
* The NVIDIA drivers I'm using are of the version 4.17.00.24, not exactly the last ones.
* As for the hardware acceleration slider, I have it in "full acceleration". Didn't touch that one.

As you can see, I'm of the school of "if it ain't broke don't fix it"...

[no_operation]

Most probably, Media Player / DirectShow is not using the hardware overlay, and is using direct RGB output with software scaling. Unfortunately, DirectShow often turns off overlay without any obvious reason. The DivX decoder uses some tricks to enforce overlay display in these cases.

To test if overlay is used: Play a movie and take a screen shot. If the screen shot only shows an empty rect, the movie actually got played in an overlay buffer.

[PaulJBis]

I just made that test, and you nailed it. That's exactly what it was.

[SeeMoreDigital]

I love it when a plan comes together.