[Standards] SIMS issues

Jonas Schäfer jonas at wielicki.name
Sat Sep 7 11:29:13 UTC 2019

On Mittwoch, 19. Juni 2019 19:46:02 CEST Sergey Ilinykh wrote:
> Hi
> I mostly implemented SIMS in Psi and see next problems
> 1) The requirement for top-level reference element looks strange.
>    In Most of the case when I want to share something, I don't want to
> refer to anything.
>    If I really want to have a reference I would add it inside of
> <media-sharing>.
> 2) Top-level reference doesn't state what has to be in "uri" which is
> required
> 3) Seems like only one <media-sharing> element is allowed while it's quite
> common to share multiple files at once with just one description. Sending
> each shared file via separate stanza doesn't look to be a good option since
> servers often limit sending rate and separate stanzas somehow corrupt
> logical scope.
> 4) I want to use SIMS for voice messages but there is no any metadata for
> audio.
>    I need at least duration and amplitude diagram there. Something like
> following would be really
>    nice to have:
>    <audio>
>       <tune xmlns='http://jabber.org/protocol/tune'>tune data here</tune>
>       <spectrum coding="u8">0,3,135,237,210,195,243,137,...,4,4,1</spectrum>
> </audio>

Nitpick: If you are going to implement this and intend on standardising it, 
may I suggest to use base64-encoded u8 bytes instead of the proposed string 
syntax? It will be smaller by approximately 63% for uniformly distributed 
amplitudes and by approximately 33% for all-zeros (worst-case). (I am also 
fairly certain that for the preview, u8 is fully sufficient.) (base64 starts 
to be consistently smaller (in the all-zeros worst-case) once you have more 
than 5 samples.)

Another Nitpick: From your description, it is more like an <amplitudes/> 
preview instead of a <spectrum/> (which implies something like a Fourier 
transform or another way to obtain per-frequency values).

kind regards,
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