From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f46.google.com (mail-ej1-f46.google.com [209.85.218.46]) by mx.groups.io with SMTP id smtpd.web09.316.1618595707805179048 for ; Fri, 16 Apr 2021 10:55:08 -0700 Authentication-Results: mx.groups.io; dkim=pass header.i=@gmail.com header.s=20161025 header.b=EOJix7CT; spf=pass (domain: gmail.com, ip: 209.85.218.46, mailfrom: harlydavidsen@gmail.com) Received: by mail-ej1-f46.google.com with SMTP id sd23so34700776ejb.12 for ; Fri, 16 Apr 2021 10:55:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=LDGZP/6kmMm+we3KM9+ewhBzUIJrBvsinG6emjDNS+M=; b=EOJix7CTl0Yn0I4tJdF0eMWRJ1f8wMAuhU238xaPRg/U9bjv0wZpMhZ4gPxzSBfKb4 B7SLrDnDrzPJdY++fDUt1+kZDq2EryvYQnr5+yO5tRXbVl/eQ+9ADf165OG4s17GVC3c FK28kUvn2t+Y0gU2lMkL3w31Oi7geb75210nU43siolxW/A3YOSrrvPQUybQjXuStDTV GB8kGijH/w1AEKY10mRsFmXSP80VaGx/HGuePSvAavvAxxU1HwkeEI2W5Q/hVaT78ugX uLFV+wpFLqxJNZa3RcIEKqVI8JJ91UmrtnBdgFJNiPlU0zDLSAwcWdz8fNduFWhhev6i k1xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=LDGZP/6kmMm+we3KM9+ewhBzUIJrBvsinG6emjDNS+M=; b=nahcy0PLdDpiI5Bp9NYkMaK5RY3cR3gLo46nqpgHkkhHm+Lk4i7HxSDc4RuQRLYc0z I/R2n8Bu5iPcrbx/Csy8NGn//XYPtzWBY1btVzjUK30O5EKX3sd2GI4iO+CDk2fsn6MA 2pCT9KsZdtme1quF2UI/EvzamzwwCm8PFrwELEX3Y1DUZAHkxaP/nmwNOTvAzPoCuYkE VK4MeLy+8bwiExOB2JHhB7FESJzNSihKpr1XC5wfjfswv68DynbCKVGxwyoaUu0iLLNQ uA695hsaEKvm+NSUF9gG5GkOBXAE4KaP+vpbTsG2HUM3DieCwKvaBNJVCDuvaILAv2mG 1tpA== X-Gm-Message-State: AOAM530KeXh3gaseRKZTM9fJfgBjW7X5Yf0elic6utk1mcqBWgb/fx3a fHltfJmDoPpudtWsFxbx88vaJS0KML5q/UXTs9k= X-Google-Smtp-Source: ABdhPJxhWN4mB3ZA6XEJ6pEW30b+YcWpiquzGvRRkxweNUV0qhynTFQNEEegsRiWaI07Yg9h0v+AtbAu8wWUOm4McV0= X-Received: by 2002:a17:906:48c4:: with SMTP id d4mr9782669ejt.548.1618595706277; Fri, 16 Apr 2021 10:55:06 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:ab4:a64c:0:0:0:0:0 with HTTP; Fri, 16 Apr 2021 10:55:05 -0700 (PDT) In-Reply-To: References: <4AEC1784-99AF-47EF-B7DD-77F91EA3D7E9@apple.com> <309cc5ca-2ecd-79dd-b183-eec0572ea982@ipxe.org> <33e37977-2d27-36a0-89a6-36e513d06b2f@ipxe.org> <6F69BEA6-5B7A-42E5-B6DA-D819ECC85EE5@apple.com> <20210416113447.GG1664@vanye> <10E3436C-D743-4B2F-8E4B-7AD93B82FC92@apple.com> From: "Ethin Probst" Date: Fri, 16 Apr 2021 12:55:05 -0500 Message-ID: Subject: Re: [edk2-devel] VirtIO Sound Driver (GSoC 2021) To: Andrew Fish Cc: edk2-devel-groups-io , Leif Lindholm , Michael Brown , Mike Kinney , Laszlo Ersek , "Desimone, Nathaniel L" , Rafael Rodrigues Machado , Gerd Hoffmann Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Also, forgot to add this before sending: yes, speech synthesizers usually generate the PCM audio on the fly. They can write it to an output file, but if your just using it in a screen reader, then you end up streaming it to the audio device. This raises another issue I was pondering, but I (don't think) we need to handle that quite yet. The problem involves output generated by the HII, console, etc.: when we're using a speech synthesizer, it might be configured to speak at a faster or slower rate depending on the preferences of the user (we definitely want to let the user control these things because different people have different preferences on the speed of speech synthesizers: some can understand it at really fast rates and others can't, for example). The problem arises when we want to forward output from the screen (say, the simple text output protocol). Assume that a user is running the EFI shell as an example, which, if I'm not mistaken, uses this protocol. The shell calls EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.OutputString(). We probably then want this function to forward the string passed in onto the speech synthesizer, assuming that accessibility features are enabled (I'm assuming we'd want to make that a toggle). The problem is that one can call EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.OutputString() many times. During all these calls, text is being sent to the synthesizer, its generating samples, and forwarding those samples onto the audio output protocol. The problem is: how do we ensure that these samples don't overlap or cause other problems (e.g.: interrupt streams that are still being processed)? As I said, these are things we don't need to necessarily consider now, but this is a problem we'll need to tackle in the future. On 4/16/21, 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 enabl= e > 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? > > 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=E2=80=99m 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 forma= t >>>>>>> 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 requireme= nt >>>>>> 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 extern= al >>>>>> 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 mor= e >>>>> that >>>>> flexibility. >>>>> >>>>> How about another use case. Lets say the Linux OS loader (Grub) want= s >>>>> 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 Lin= ux >>>>> 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 yo= u >>>>> use >>>>> may impact the quality of the playback for a given board. Your EFI i= s >>>>> 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. S= o >>>>> that >>>>> will required testing, and some one with audiophile ears (or an AI >>>>> program) >>>>> to test all the combinations. I=E2=80=99m not kidding I get BZs on t= he 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-ti= me >>>>>> firmware. :) >>>>>> >>>>> >>>>> I think that got a little too simple I=E2=80=99d go back and look at= the >>>>> example >>>>> I >>>>> posted to the thread but add an API to load the buffer, and then pla= y >>>>> 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 i= n >>>>> 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 doe= s >>>>> 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 conscio= us >>>>> as we >>>>> need to treat the Audo file as attacker controlled data. >>>>> >>>>> Thanks, >>>>> >>>>> Andrew Fish >>>>> >>>>>> Michael >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Signed, >>>> Ethin D. Probst >>> >>> >>>=20 >>> >>> >> >> > > > -- > Signed, > Ethin D. Probst > --=20 Signed, Ethin D. Probst