> On Apr 16, 2021, at 10:45 AM, Ethin Probst wrote: > > Yes, three APIs (maybe like this) would work well: > - Start, Stop: begin playback of a stream > - SetVolume, GetVolume, Mute, Unmute: control volume of output and enable muting > - CreateStream, ReleaseStream, SetStreamSampleRate: Control sample > rate of stream (but not sample format since Signed 16-bit PCM is > enough) > Marvin, how do you suggest we make the events then? We need some way > of notifying the caller that the stream has concluded. We could make > the driver create the event and pass it back to the caller as an > event, but you'd still have dangling pointers (this is C, after all). > We could just make a IsPlaying() function and WaitForCompletion() > function and allow the driver to do the event handling -- would that > work? > Ethin, I can adapt my example from earlier in the thread for how to do async EFI APIs. /** The struct of Audio Token. **/ typedef struct { /// /// Event will be signaled when the read audo has been played. /// If only synchronous playback is supported the Event must still get signaled. /// EFI_EVENT Event; /// /// Defines whether or not the signaled event encountered an error. /// EFI_STATUS TransactionStatus; } CODE_FIRST_HDA_AUDIO_TOKEN; /** Play synchronous or asynchronous audio. If Token is passed in the audio is played asynchronously, if Token is NULL then this call blocks until the Audio is complete. @param[in] This A pointer to the CODE_FIRST_HDA_AUDIO_PROTOCOL instance. @param[in, out] Token A pointer to the token associated with the transaction. If NULL this functions blocks until audio play back is complete. @retval EFI_SUCCESS The audio started playing. @retval EFI_OUT_OF_RESOURCES The request could not be completed due to a lack of resources. @retval EFI_INVALID_PARAMETER One or more parameters are invalid. **/ typedef EFI_STATUS (EFIAPI *CODE_FIRST_HDA_AUDIO_PROTOCOL_PLAY_STREAM)( IN CODE_FIRST_HDA_AUDIO_PROTOCOL *This, IN OUT CODE_FIRST_HDA_AUDIO_TOKEN *Token OPTIONAL ); You can fake out the asynchronous interface in your synchronous flow by …. if (Token != NULL) { Token->TransactionStatus = Status; // return value from sync call gBS->SignalEvent (Token->Event); } This just gives the caller the experience that the event was signaled before the call returned, which is legal for an async API. The caller allocates a CODE_FIRST_HDA_AUDIO_TOKEN and creates an Event that has an associated callback function. Then calls gAudio->PlayStream (gAudio, Token); and the callers callback function fires when the audio stream completes. Thanks, Andrew Fish > On 4/16/21, Andrew Fish wrote: >> >> >>> On Apr 16, 2021, at 4:34 AM, Leif Lindholm wrote: >>> >>> Hi Ethin, >>> >>> I think we also want to have a SetMode function, even if we don't get >>> around to implement proper support for it as part of GSoC (although I >>> expect at least for virtio, that should be pretty straightforward). >>> >> >> Leif, >> >> I’m think if we have an API to load the buffer and a 2nd API to play the >> buffer an optional 3rd API could configure the streams. >> >>> It's quite likely that speech for UI would be stored as 8kHz (or >>> 20kHz) in some systems, whereas the example for playing a tune in GRUB >>> would more likely be a 44.1 kHz mp3/wav/ogg/flac. >>> >>> For the GSoC project, I think it would be quite reasonable to >>> pre-generate pure PCM streams for testing rather than decoding >>> anything on the fly. >>> >>> Porting/writing decoders is really a separate task from enabling the >>> output. I would much rather see USB *and* HDA support able to play pcm >>> streams before worrying about decoding. >>> >> >> I agree it might turn out it is easier to have the text to speech code just >> encode a PCM directly. >> >> Thanks, >> >> Andrew Fish >> >>> / >>> Leif >>> >>> On Fri, Apr 16, 2021 at 00:33:06 -0500, Ethin Probst wrote: >>>> Thanks for that explanation (I missed Mike's message). Earlier I sent >>>> a summary of those things that we can agree on: mainly, that we have >>>> mute, volume control, a load buffer, (maybe) an unload buffer, and a >>>> start/stop stream function. Now that I fully understand the >>>> ramifications of this I don't mind settling for a specific format and >>>> sample rate, and signed 16-bit PCM audio is, I think, the most widely >>>> used one out there, besides 64-bit floating point samples, which I've >>>> only seen used in DAWs, and that's something we don't need. >>>> Are you sure you want the firmware itself to handle the decoding of >>>> WAV audio? I can make a library class for that, but I'll definitely >>>> need help with the security aspect. >>>> >>>> On 4/16/21, Andrew Fish via groups.io wrote: >>>>> >>>>> >>>>>> On Apr 15, 2021, at 5:59 PM, Michael Brown wrote: >>>>>> >>>>>> On 16/04/2021 00:42, Ethin Probst wrote: >>>>>>> Forcing a particular channel mapping, sample rate and sample format >>>>>>> on >>>>>>> everyone would complicate application code. From an application point >>>>>>> of view, one would, with that type of protocol, need to do the >>>>>>> following: >>>>>>> 1) Load an audio file in any audio file format from any storage >>>>>>> mechanism. >>>>>>> 2) Decode the audio file format to extract the samples and audio >>>>>>> metadata. >>>>>>> 3) Resample the (now decoded) audio samples and convert (quantize) >>>>>>> the >>>>>>> audio samples into signed 16-bit PCM audio. >>>>>>> 4) forward the samples onto the EFI audio protocol. >>>>>> >>>>>> You have made an incorrect assumption that there exists a requirement >>>>>> to >>>>>> be able to play audio files in arbitrary formats. This requirement >>>>>> does >>>>>> not exist. >>>>>> >>>>>> With a protocol-mandated fixed baseline set of audio parameters >>>>>> (sample >>>>>> rate etc), what would happen in practice is that the audio files would >>>>>> be >>>>>> encoded in that format at *build* time, using tools entirely external >>>>>> to >>>>>> UEFI. The application code is then trivially simple: it just does >>>>>> "load >>>>>> blob, pass blob to audio protocol". >>>>>> >>>>> >>>>> >>>>> Ethin, >>>>> >>>>> Given the goal is an industry standard we value interoperability more >>>>> that >>>>> flexibility. >>>>> >>>>> How about another use case. Lets say the Linux OS loader (Grub) wants >>>>> to >>>>> have an accessible UI so it decides to sore sound files on the EFI >>>>> System >>>>> Partition and use our new fancy UEFI Audio Protocol to add audio to the >>>>> OS >>>>> loader GUI. So that version of Grub needs to work on 1,000 of different >>>>> PCs >>>>> and a wide range of UEFI Audio driver implementations. It is a much >>>>> easier >>>>> world if Wave PCM 16 bit just works every place. You could add a lot of >>>>> complexity and try to encode the audio on the fly, maybe even in Linux >>>>> proper but that falls down if you are booting from read only media like >>>>> a >>>>> DVD or backup tape (yes people still do that in server land). >>>>> >>>>> The other problem with flexibility is you just made the test matrix >>>>> very >>>>> large for every driver that needs to get implemented. For something as >>>>> complex as Intel HDA how you hook up the hardware and what CODECs you >>>>> use >>>>> may impact the quality of the playback for a given board. Your EFI is >>>>> likely >>>>> going to pick a single encoding at that will get tested all the time if >>>>> your >>>>> system has audio, but all 50 other things you support not so much. So >>>>> that >>>>> will required testing, and some one with audiophile ears (or an AI >>>>> program) >>>>> to test all the combinations. I’m not kidding I get BZs on the quality >>>>> of >>>>> the boot bong on our systems. >>>>> >>>>> >>>>>>> typedef struct EFI_SIMPLE_AUDIO_PROTOCOL { >>>>>>> EFI_SIMPLE_AUDIO_PROTOCOL_RESET Reset; >>>>>>> EFI_SIMPLE_AUDIO_PROTOCOL_START Start; >>>>>>> EFI_SIMPLE_AUDIO_PROTOCOL_STOP Stop; >>>>>>> } EFI_SIMPLE_AUDIO_PROTOCOL; >>>>>> >>>>>> This is now starting to look like something that belongs in boot-time >>>>>> firmware. :) >>>>>> >>>>> >>>>> I think that got a little too simple I’d go back and look at the example >>>>> I >>>>> posted to the thread but add an API to load the buffer, and then play >>>>> the >>>>> buffer (that way we can an API in the future to twiddle knobs). That >>>>> API >>>>> also implements the async EFI interface. Trust me the 1st thing that is >>>>> going to happen when we add audio is some one is going to complain in >>>>> xyz >>>>> state we should mute audio, or we should honer audio volume and mute >>>>> settings from setup, or from values set in the OS. Or some one is going >>>>> to >>>>> want the volume keys on the keyboard to work in EFI. >>>>> >>>>> Also if you need to pick apart the Wave PCM 16 byte file to feed it into >>>>> the >>>>> audio hardware that probably means we should have a library that does >>>>> that >>>>> work, so other Audio drivers can share that code. Also having a library >>>>> makes it easier to write a unit test. We need to be security conscious >>>>> as we >>>>> need to treat the Audo file as attacker controlled data. >>>>> >>>>> Thanks, >>>>> >>>>> Andrew Fish >>>>> >>>>>> Michael >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Signed, >>>> Ethin D. Probst >>> >>> >>> >>> >>> >> >> > > > -- > Signed, > Ethin D. Probst