How to detect an output filter

[rse]

Hi!

I´m programming my own media player with Lazarus using DShow without any manipulation of the filter graph. Mostly either the graph cannot be built or it plays fine, but sometimes it can be built but doesn´t play anyways. For example a m3u-file will build a graph but won´t play. The only filter in the chain is the ram source filter, no output, nothing. Problem is: The filter chain has a length, but it won´t progress so that it never comes to an end.

I want to detect such behavior and kick this file from the playlist, like the files that won´t build a filterchain at all. But how can I detect it? I can only think of one thing: Testing the filter chain for output-devices like "Video Renderer", "Default DirectSound Device" or "DSound Renderer". There is only one catch: How can I be sure to detect _any_ output filter that outputs sound or video? There may be others probably. Probably they have other names in other language windows systems (which could be no problem if I tested for the CLSID instead...). If so, I would probably kick an otherwise working file. Do you have any suggestions?

[JohnnyMalaria]

QueryInterface for IBasicVideo or IBasicAudio would probably work.

[rse]

Reading the remarks on
http://msdn.microsoft.com/archive/default.asp?url=/archive/en-us/directx9_c/directx/htm/defaultdirectsounddevicefilter.asp
I think that a test for either "DirectSound Renderer" or any filter in the category "CLSID_AudioRendererCategory" will cover any possible audio output filter. Probably the "CLSID_MidiRendererCategory" needs to be included, too. For Video there seems to be no Category and the "Video Renderer" filter seems to be the only video output filter. Would it be possible that there was any (proprietary) other non-windows output filter which wasn´t in one of these categorys and therefore wouldn´t be covered by this test?

Assuming that the CLSID won´t change in different versions of DShow I think probably a search for a matching CLSID in the filter chain would be faster and not less appropriate than the test for an IBasicVideo or IBasicAudio interface, because according to the documentation these are only implemented by the "Video Renderer" filter and the "Audio Renderer (WaveOut)" and "DirectSound Renderer" filter. What do you think? I´m only a newbie in DShow programming ;-)

[JohnnyMalaria]

I had thought about the CLSID_xxxx option but wondered if a filter might exist that is not registered as one of the standard filter categories.

Certainly, testing for any of the ones listed in the MS documentation would help. If none show up, querying the graph for IBasicAudio and IBasicVideo would tell you if any filters are present that renderer audio or video.

BTW, are you using Render() to create the downstream graph? If you are and you want to force DirectShow to use a specific filter (instead of the default ones), you can use RenderEx()

[rse]

Testing for IBasicAudio or IBasicVideo only if no matching CLSID is found is a great idea! That gives good performance if everything is good and it´s very tough if something might be wrong.

The goal of this player was to use DirectShow with as less intervention as possible. So I will continue to use Render(). The only thing where RenderEx() would be needed would be a possibility for the user to build its own filter graphs by hand with an interface similar to graphedit, but that´s only probably planned for the future ;-)