directX vs direct3D

[dbrb2]

Hi,

I have a machine which spends all day displaying multiple video streams in multiple VLC windows. For each, using command line parameters, I can select either directX or direct3D. I am currently running VLC 1.17.

The only outward difference I can see is that using directX uses overlays, wheras using directX does not. Does this mean then that when using dirext3D all of the video decoding is being done by the CPU as opposed to the GPU? This may nopt matter, but I'm just trying to work out the pros/cons of using one vs the other.

[Jean-Baptiste Kempf]

Both are using the GPU to do chroma conversion and scaling.

[dbrb2]

Oh good - I had worried that since, as I understand it, hardware video overlays bypass the OS (hence why screenshots / vnc servers etc see those video streams as black squares), and since this is not a problem with direct3D, this indicated the OS was having to do more work.

Seems to be working OK for now though (w7 32 bit machines)

[dbrb2]

...I notice that if I do not force an output module, then VLC chooses the "best" module to use. Does anyone know on what basis this choice is made?

We have some XP machines, and if we force direct3D, the logs show a direct3D initialisation failure, and we get no video, but directX works fine. I guess this is something to do with the installed graphics card? For the moment ihave stopped forcing the output module at all, since VLC seems to make the right choices on it's own...

[Jean-Baptiste Kempf]

...I notice that if I do not force an output module, then VLC chooses the "best" module to use. Does anyone know on what basis this choice is made?

We have some XP machines, and if we force direct3D, the logs show a direct3D initialisation failure, and we get no video, but directX works fine. I guess this is something to do with the installed graphics card? For the moment ihave stopped forcing the output module at all, since VLC seems to make the right choices on it's own...

DirectX is the default on XP
Direct3D is the default on Vista, 7 and 8

If direct3D does not work on XP for you, your drivers are screwed.

[dbrb2]

We are using some rather ancient analogue video output graphics cards on the XP machine, and we know there are some bugs in the drivers, so this sounds quite possible. Whether or not direct3d works is presumably down to what the OS can instruct the graphics hardware to do, and thus as you say the drivers?

Is there any particuloar reason why the default has changed from XP to Win7? Does direct3D have advantages?

[Jean-Baptiste Kempf]

If you do not know why, don't change the defaults.

[dbrb2]

Thanks for your polite and informative response