[wdmaudiodev] Re: Retrieving WAVEFORMATEX from IAudioSessionControl
- From: Dadi <dadiku@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Wed, 17 Dec 2014 23:20:58 +0200
Got it, thank you.
2014-12-17 23:03 GMT+02:00 Matthew van Eerde <
Matthew.van.Eerde@xxxxxxxxxxxxx>:
> > I thought maybe there is a runtime attribute that we can read from
> IAudioSessionControl and get the audio format?
>
> > Or maybe we can QueryInterface to get some other class to assist?
>
>
>
> Sorry, no such mechanism exists. The only two ways to get the WAVEFORMATEX
> for an active stream are:
>
> (a) Be the player – the player knows the WAVEFORMATEX because it
> handed it to WASAPI in the first place
>
> (b) Be the SFX; players will call IAudioClient::IsFormatSupported,
> which bubbles up to a format support call on the SFX
>
>
>
> *From:* wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:
> wdmaudiodev-bounce@xxxxxxxxxxxxx] *On Behalf Of *Dadi
> *Sent:* Wednesday, December 17, 2014 12:57 PM
>
> *To:* wdmaudiodev@xxxxxxxxxxxxx
> *Subject:* [wdmaudiodev] Re: Retrieving WAVEFORMATEX from
> IAudioSessionControl
>
>
>
> Hi Matthiew,
>
> The upmix effect is integrated along with other effects we have for
> surround and we cannot separate it to two different effects SFX and MFX.
>
> We will check for the minimum and/or maximum number of channels and also
> analyze the audio stream for our calculations.
>
> In any case, my original question was not only for upmix but also for
> other different effects (the upmix effect is only one example) in which we
> need to get the WAVEFORMATEX of the active streams.
>
> I thought maybe there is a runtime attribute that we can read from
> IAudioSessionControl and get the audio format?
>
> Or maybe we can QueryInterface to get some other class to assist?
>
>
> So we need to find the best way to retrieve this information. We prefer to
> avoid writing orphan SFX APOs only for that matter.
>
> Thank you,
>
> Dadi
>
>
>
>
>
> 2014-12-17 22:40 GMT+02:00 Matthew van Eerde <
> Matthew.van.Eerde@xxxxxxxxxxxxx>:
>
> > our effects must all reside in the same APO instance
>
>
>
> Can you elaborate on why?
>
>
>
> The approach we had in mind when designing the system is to do most
> processing in the MFX; processing where the channel count may change in the
> SFX; and hardware compensation in the EFX.
>
>
>
> For example, you could create an SFX that did both 2.0 => 5.1 upmix and
> 5.1 => 5.1 passthrough.
>
>
>
> It should be fine to have out-of-band communication between your SFX and
> your MFX. What would do you do in your MFX if there were two active
> streams, one with a stereo WAVEFORMATEX, and one with a 5.1 WAVEFORMATEX?
>
>
>
> *From**:* wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:
> wdmaudiodev-bounce@xxxxxxxxxxxxx] *On Behalf Of* Dadi
> *Sent**:* Wednesday, December 17, 2014 12:30 PM
>
>
> *To:* wdmaudiodev@xxxxxxxxxxxxx
> *Subject:* [wdmaudiodev] Re: Retrieving WAVEFORMATEX from
> IAudioSessionControl
>
>
>
> Hi Matthew,
>
> Yes we know that but we are processing only global (MFX) and our effects
> must all reside in the same APO instance so in surround we get only 5.1
> => 5.1.
> In addition we are also working on new effects (not upmix) and we must
> have the WAVESFORMTEX of the active streams.
>
> The possibilities we currently have are:
> - We can write SFX APOs that always do full bypass only for that matter -
> gather the WAVESFORMATEX information and copy it to a shared memory or some
> other IPC mechanism so the MFX APO can read read it.
>
> - We can also get the assistance of the codec vendor (with private API)
> to give us this information to overcome this limitation but we prefer to
> have a better way for this.
>
>
>
> Is there any way to resolve it gracefully?
>
> Thank you,
>
> Dadi
>
>
>
> 2014-12-17 20:08 GMT+02:00 Matthew van Eerde <
> Matthew.van.Eerde@xxxxxxxxxxxxx>:
>
> It’s too late to do any kind of stream-intelligent upmixing in a render
> GFX, MFX or EFX. Everything’s already been channel-converted and mixed
> together by the time it gets to you. If you want to do intelligent channel
> matrixing per stream, you need an SFX.
>
>
>
> Render SFXes (and only render SFXes) can support multiple input formats,
> even with differing channel counts. So on a 5.1 output you can do:
>
> 1. 2.0 => 5.1 (upmix)
>
> 2. 5.1 => 5.1
>
>
>
> And on a 2.0 output, you can do:
>
> 1. 2.0 => 2.0
>
> 2. 5.1 => 2.0 (downmix)
>
>
>
> *From**:* wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:
> wdmaudiodev-bounce@xxxxxxxxxxxxx] *On Behalf Of* Dadi
> *Sent**:* Tuesday, December 16, 2014 6:02 AM
> *To**:* wdmaudiodev@xxxxxxxxxxxxx
> *Subject**:* [wdmaudiodev] Re: Retrieving WAVEFORMATEX from
> IAudioSessionControl
>
>
>
> Hi Matthew,
>
> Our global APO needs that information for its processing logic.
>
> E.g. for doing surround upmix we need to know the channel count of all
> open sessions. That way we can find if an app opened a stereo channel to
> play audio (and so the APO should do upmix) or if an app is playing full
> surround and intentionally only two channels are active (e.g. can happen
> while a movie is played) and in this case we should NOT do any upmix in the
> APO.
>
> Because there can be many audio sessions simultaneous then we will take
> the minimum or maximum values for reference.
>
> The above is only one example and there are other cases in which our APO
> needs to know the original format.
>
> Windows API allows us to enumerate all the active audio sessions (we can
> filter it per endpoint) and get IAudioSessionControl for each session but
> we need to use it to get the active WAVESFORMATEX.
>
>
>
> Note - we do not have any SFX APOs, only global.
>
> Is there any way to resolve this?
>
> Thank you,
>
> Dadi
>
>
>
>
>
>
>
> 2014-12-15 18:58 GMT+02:00 Matthew van Eerde <
> Matthew.van.Eerde@xxxxxxxxxxxxx>:
>
> Conceptually, an audio session (IAudioSessionControl) is an (app,
> endpoint) pair.
>
>
>
> An app can have zero or more active streams (IAudioClient) on a given
> endpoint at any given time.
>
>
>
> The stream has an associated WAVEFORMATEX (what was passed to
> IAudioClient::Initialize) but there’s no way to retrieve it from the
> IAudioClient.
>
>
>
> There is also no way to get the list of active IAudioClients from an
> IAudioSessionControl.
>
>
>
> What is the larger problem you’re trying to solve?
>
>
>
> *From**:* wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:
> wdmaudiodev-bounce@xxxxxxxxxxxxx] *On Behalf Of* Dadi
> *Sent**:* Sunday, December 14, 2014 11:21 AM
> *To**:* wdmaudiodev@xxxxxxxxxxxxx
> *Subject**:* [wdmaudiodev] Retrieving WAVEFORMATEX from
> IAudioSessionControl
>
>
>
> Hi,
>
> Is it possible to retrieve the audio session format (WAVEFORMATEX) from a
> given pointer to an active IAudioSessionControl?
>
> Thank you,
>
> Dadi
>
>
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