[edk2-devel] VirtIO Sound Driver (GSoC 2021)
Michael Brown
mcb30 at ipxe.org
Fri Apr 16 00:59:26 UTC 2021
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".
> 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. :)
Michael
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