Query supported MIME types from MHI

[TomSoniq]

Hi all,


MHI was originally developed as an easy to use interface to send MPEG audio data (mainly layer 2 and layer 3 a.k.a. mp2 and mp3) to a mp2/mp3-only hardware decoder. (This is where the M in MHI comes from )


Nowadays more advanced hardware decoders have become available like the one on the Prisma Megamix. So MHI has evolved into a standard for sending all sorts of compressed audio to a hardware decoder.


But the application using it can't know which formats are actually supported by the corresponding hardware. It can only make a guess or simply send any data hoping that it would work. Not a good long term solution.


So what about adding a new query tag to MHIQuery() which returns a list of supported audio formats?


To make this open to the future I'd suggest it simply returns a comma-separated list of MIME types.


This is still a little ambiguous because MIME types tend to specify the container rather than the CODEC. Hence it might make sense to create a sub-list for each container and list the specific codecs in it like:

audio/mpeg{audio/mp2,audio/mp3}

or

audio/ogg{audio/vorbis,audio/opus}

and hardware modules that can do vorbis but can't do opus could list:

audio/ogg{audio/vorbis}

These sub-lists lead us to MPEG-4 audio a.k.a. m4a which also can contain various formats like ALS, CELP and Direct Stream Transfer but mainly AAC.


So a hardware decoder that supports AAC contained in MP4 (which is ADIF) but also as a raw AAC-ADTS stream could list

audio/mp4{audio/aac},audio/aac

So the response for MAS3507D based players would simply be:

audio/mpeg{audio/mp2,audio/mp3}

But VS1063 based players like the Prisma Megamix would at least reply:

audio/mpeg{audio/mp2,audio/mp3},audio/ogg{audio/vorbis},audio/mp4{audio/aac},audio/aac,audio/flac,audio/x-ms-wma

What do you think?

[kriz]

Somehow this topic went unanswered, but it would be very nice to have these options for the different formats... Also makes higher potential for new cards or productions

[TomSoniq]

I've uploaded a new dev archive to Aminet which supports this:
http://aminet.net/driver/audio/mhi_dev.lha