7 Jan
2003
7 Jan
'03
2:58 a.m.
My understanding of VVID's is that the sequencer puts one complete,
continuous note on a particular VVID. The sequencer only reuses a VVID once
it has ended any previous notes on that VVID. The sequencer can allocate a
large number of VVIDs so that it never has to make a voice stealing decision
on its end (and so we don't have to make roundtrips). This large allocation
means that the plugin should never try to allocate a significant sized
structure for each VVID. Instead, the plugin should match VVIDs to actual
voices as incoming voice-on messages are received until all actual voices
are used. After all voices are in use, the plugin has to decide whether to
steal voices from ongoing notes or deny voice-on events. Voice stealing
decisions are properly made by the plugin. This is the case even if the
sequencer knows how many actual voices there are because the plugin has much
more intimate knowledge of the nature of the voices: their amplitude, timbre
etc.
My underlying assumptions are:
-a single object resides in each channel, be it a piano a gong or whatever,
there is one in the channel
-HOWEVER, that single object may be polyphonic; the piano may be able to
sound multiple notes concurrently, the gong may be able to sound two quick
strokes in succession which overlap in their duration.
-DEFINITION: We call the facility for making ONE of those sounds a voice.
-DEFINITION: the individual voices produce finite periods of sound which we
call notes. A note is the sound that a voice makes between a Voice-On event
and a Voice-Off event (provided that the voice is not reappropriated in the
middle to make a different note)
-HOWEVER- there is no rule that a note has any pitch or velocity or any
other particular parameter, it is just that the Voice-On tells the voice to
start making sound and the Voice-Off tells the voice to stop making sound.
-ALSO HOWEVER- the entity which sends voice-on and off messages may not
directly refer to the object's voices. Instead, the event sender puts
separate notes on separate Virtual Voice IDs to indicate what it desires the
voices to do. This differential is in place because sequencers typically
send more concurrent notes than the plugin has actual voices for AND the
plugin is better suited to decide how to allocate those scarce resources. In
other words, it is the role of the plugin to decide whether or not to steal
a voice for a new note and which voice to steal. So the sequencer sends out
notes in fantasy-land VVID notation where they never ever have to overlap,
and the plugin decides how best to play those notes using the limited number
of voices it has.
As I see it, the procedure for using a voice via a particular VVID is as
follows (note that all events mentioned are assumed to have a particular
VVID):
(1)send voice-on event at timestamp X. This indicates a note is to start.
(2)send parameter-set events also at timestamp X, these are guaranteed to
follow the voice-on event even though they have the same timestamp because
the event ordering specifies it. These parameter-set events are to be
considered voice initializers should the plugin support such a concept,
otherwise they are the first regular events to effect this note.
(3)send parameter-set events at later times to modify the note as it
progresses.
(4)send voice-off event at later time to end the note and free the voice.
When the plugin reads the voice-on event at timestamp X it decides whether
to allocate a voice or not. If it has an initialization routine for voice-on
events, then the plugin must read through the remaining events with
timestamp X to get initialization arguments. The plugin must delay actually
initializing the voice until it has read the other events at the same
timestamp as the voice-on event. If the plugin doesn't do any special
initialization procedures then it doesn't have to worry about this because
the events concurrent with the voice-on event can just be applied in the
same manner as later param-set events.
--jacob robbins:..... soundtank..........
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7 Jan
7 Jan
4:21 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
continuous note on a particular VVID. The sequencer
only reuses a VVID once
it has ended any previous notes on that VVID. The sequencer can allocate a
This is the current issue at hand - just because the sequencer has ended a
VVID with a voice-off, doesn't mean the voice is off. It just begins the
release phase of the envelope, on some synths. This could take a while.
Either you need to NEVER re-use a VVID, or you need to tell the host when an
ended VVID is actually re-usable. Or you need to have voice-ids allocated
by the plugin, and NOT the host, which I like more.
My underlying assumptions are:
I made a post a while back defining all the XAP terminology to date. Read
it if you haven't - it is useful :)
-DEFINITION: the individual voices produce finite
periods of sound which we
call notes. A note is the sound that a voice makes between a Voice-On event
and a Voice-Off event (provided that the voice is not reappropriated in the
middle to make a different note)
We've been avoiding the word 'note' because it is too specific. The
lifetime of voice is either finite or open-ended. A synth would be
open-ended. A gong hit would be finite.
-HOWEVER- there is no rule that a note has any pitch
or velocity or any
other particular parameter, it is just that the Voice-On tells the voice to
start making sound and the Voice-Off tells the voice to stop making sound.
Correct. Though David is half-heartedly arguing that maybe Velocity is the
true note-on. I disagree.
-ALSO HOWEVER- the entity which sends voice-on and off
messages may not
directly refer to the object's voices. Instead, the event sender puts
..in the currently understood VVID model.
voices to do. This differential is in place because
sequencers typically
send more concurrent notes than the plugin has actual voices for AND the
On the contrary, hopefully you will rarely exceed the max polyphony for each
instrument.
other words, it is the role of the plugin to decide
whether or not to steal
I believe you should always steal notes, but I suppose there will be some
instrument plugin some lunatic on here will devise that does not follow
that. Newer notes are always more important than older notes, but if you
exceed max poly, a red light should go off!
(1)send voice-on event at timestamp X. This indicates
a note is to start.
(2)send parameter-set events also at timestamp X, these are guaranteed to
This is also for debate - David dislikes (and I agree) the notion that you
have to send a note-on but the plugin does not have enough info to handle
(for example) a velocity-mapped sampler until later. Process events in
order. So a few ideas are on the table.
(4)send voice-off event at later time to end the note
and free the voice.
And what of step-sequencing, where you send a note-on and never a note-off?
Finite duration voices (samples, drum hits, etc) end spontaneously. Does
the plugin tell the host about it, or just let the VVID leak?
When the plugin reads the voice-on event at timestamp
X it decides whether
to allocate a voice or not. If it has an initialization routine for voice-on
events, then the plugin must read through the remaining events with
timestamp X to get initialization arguments. The plugin must delay actually
I guess it may not be tooo bad. Plugins which need some init info (such as
velocity for the velo-map) know they need this, and can look for that info.
Other plugins for whom an init event is no different than a continuous event
just go about their merry way.
But before we all decide this, I want to explore other notions. I'm not
saying my negative Voice-ID thing is great, but I rather like the idea that
Voice-Ids mean something and are almost purely the domain of the plugin.
Tim
5:35 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Tue, Jan 07, 2003 at 12:15:40 -0800, Tim Hockin wrote:
Having the plugins allocate them is a pain, its much easier if the host
aloocates them, and just does so from a sufficiently large pool, if you
have 2^32 host VVIDs per instrument you can just round robin them.
continuous
note on a particular VVID. The sequencer only reuses a VVID once
it has ended any previous notes on that VVID. The sequencer can allocate a
This is the current issue at hand - just because the sequencer has ended a
VVID with a voice-off, doesn't mean the voice is off. It just begins the
release phase of the envelope, on some synths. This could take a while.
Either you need to NEVER re-use a VVID, or you need to tell the host when an
ended VVID is actually re-usable. Or you need to have voice-ids allocated
by the plugin, and NOT the host, which I like more. This is also for debate - David dislikes (and I agree)
the notion that you
have to send a note-on but the plugin does not have enough info to handle
(for example) a velocity-mapped sampler until later. Process events in
order. So a few ideas are on the table.
You do have enough infomation, its just that it may be superseded later.
Velocity can have a default.
ONe great thing about this scheme is that it encourages people not to
think of certain, arbitary parameters as instantiation parameters, withc
are special in some way, 'cos there not.
- Steve
9:09 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Tuesday 07 January 2003 10.28, Steve Harris wrote:
[...]
Well, they *are* special in that they're latched only at certain
points. The problem is that if synths cannot effectively *implement*
it that way, it becomes the host's/sender's responsibility to know
the difference, and make sure that these controls are handled the
right way. And unless the host/sender can tell the synth exactly when
to latch the values, there is no way to get this right.
What I'm saying is that synths should preferably behave is if *all*
voice controls ever received are tracked on a per-VVID basis, so they
can be latched as intended when the synth decides to start a physical
voice. That way, you can play continous control data on latched
control synths and vice versa, without nasty side effects or "smart"
event processing in the host/sender.
Obviously, this just isn't possible if the number of VVIDs used to
control a synth is unknown or very large. However, I don't see a
reason why you would use many more VVIDs than there are physical
voices, so I don't see this as a real problem.
Synths that don't allocate physical voices as soon as a VVID gets
it's first control may have to allocate virtual voices upon
connection, but I think that's acceptable, considering the
alternatives.
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
--- http://olofson.net --- http://www.reologica.se ---
This is also
for debate - David dislikes (and I agree) the notion
that you have to send a note-on but the plugin does not have
enough info to handle (for example) a velocity-mapped sampler
until later. Process events in order. So a few ideas are on the
table.
You do have enough infomation, its just that it may be superseded
later. Velocity can have a default.
ONe great thing about this scheme is that it encourages people not
to think of certain, arbitary parameters as instantiation
parameters, withc are special in some way, 'cos there not.
2:46 p.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
ONe great thing about this scheme is that it
encourages people not to
think of certain, arbitary parameters as instantiation parameters, withc
are special in some way, 'cos there not.
The way I've seen velocity-mapped samplers is not to change the sample later
- you get the sample that maps to the initial velocity, and further changes
are just volume/filter manipulation.
8 Jan
8 Jan
6:56 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Tue, Jan 07, 2003 at 10:40:15 -0800, Tim Hockin wrote:
Ny if you map CC1 (say) to a map then changing that will change the
sample, its just that, in MIDI, velocity cant change after the voice has
started.
- Steve
ONe great
thing about this scheme is that it encourages people not to
think of certain, arbitary parameters as instantiation parameters, withc
are special in some way, 'cos there not.
The way I've seen velocity-mapped samplers is not to change the sample later
- you get the sample that maps to the initial velocity, and further changes
are just volume/filter manipulation. 
9:34 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Wed, 8 Jan 2003, Steve Harris wrote:
On Tue, Jan 07, 2003 at 10:40:15 -0800, Tim Hockin
wrote:
Ny if you map CC1 (say) to a map then changing that will change the
sample, its just that, in MIDI, velocity cant change after the voice has
started.
Not quite right, _I guess_ that in some synths you can change velocity of
a note after it has started by sending polyphonic aftertouch messages.
At least, you can use polyphinc aftertouch messages for that purpose.
--
ONe great
thing about this scheme is that it encourages people not to
think of certain, arbitary parameters as instantiation parameters, withc
are special in some way, 'cos there not.
The way I've seen velocity-mapped samplers is not to change the sample later
- you get the sample that maps to the initial velocity, and further changes
are just volume/filter manipulation.
11:46 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Wed, Jan 08, 2003 at 02:27:51PM +0100, Kjetil S. Matheussen wrote:
You can use polyphonic aftertouch to change the amplitude of a note, but
MIDI aftertouch is not the same thing as MIDI velocity, attack velocity can
only be sent with NOTE ON messages.
The case we are discussing here is when velocity is mapped to a sample
map, so differnt samples are selected depending on the velocity.
- Steve
Ny if you map
CC1 (say) to a map then changing that will change the
sample, its just that, in MIDI, velocity cant change after the voice has
started.
Not quite right, _I guess_ that in some synths you can change velocity of
a note after it has started by sending polyphonic aftertouch messages.
At least, you can use polyphinc aftertouch messages for that purpose.
5:50 p.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Wednesday 08 January 2003 14.27, Kjetil S. Matheussen wrote:
[...]
Yes, but Poly Aftertouch is not the same things as NoteOn velocity in
the MIDI protocol. Of course you can map multiple controls to the
same function, but that's a completely different matter.
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
--- http://olofson.net --- http://www.reologica.se ---
Ny if you map
CC1 (say) to a map then changing that will change
the sample, its just that, in MIDI, velocity cant change after
the voice has started.
Not quite right, _I guess_ that in some synths you can change
velocity of a note after it has started by sending polyphonic
aftertouch messages. At least, you can use polyphinc aftertouch
messages for that purpose.
5:47 p.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Wednesday 08 January 2003 11.50, Steve Harris wrote:
On Tue, Jan 07, 2003 at 10:40:15 -0800, Tim Hockin
wrote:
Ny if you map CC1 (say) to a map then changing that will change the
sample, its just that, in MIDI, velocity cant change after the
voice has started.
Right. But the synth can still latch CC1 only on NoteOn - and in that
case, you have to send CC1 *before* the NoteOn you want it to affect.
However, note that CC1 is a channel control, and thus doesn't have
the problem of "what if there's no voice allocated to trace the
controls!?"
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
--- http://olofson.net --- http://www.reologica.se ---
ONe great
thing about this scheme is that it encourages people
not to think of certain, arbitary parameters as instantiation
parameters, withc are special in some way, 'cos there not.
The way I've seen velocity-mapped samplers is not to change the
sample later - you get the sample that maps to the initial
velocity, and further changes are just volume/filter
manipulation.
3:43 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
Either you
need to NEVER re-use a VVID, or you need to tell the host when an
ended VVID is actually re-usable. Or you need to have voice-ids allocated
by the plugin, and NOT the host, which I like more.
Having the plugins allocate them is a pain, its much easier if the host
aloocates them, and just does so from a sufficiently large pool, if you
have 2^32 host VVIDs per instrument you can just round robin them.
7 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Tue, Jan 07, 2003 at 11:37:51 -0800, Tim Hockin wrote:
Why is it a pain? I think it is clean. I've never cared for the idea of
Virtual Voices. Either a voice is on, or it is not. The plugin and the
host need to agree on that.
I dont think the host doesn't has to care. Only the instrument can do
voice assignment and priority, and I think its better if assigning voices
doesn't require a two way conversation.
If hte host assigns the VVIDs then it can refer to that voice instantly,
without having to ask the instrument what ID it assigned to the voice it
just created.
- Steve
Either you need to NEVER re-use a VVID, or you need to
tell the host when an
ended VVID is actually re-usable. Or you need to have voice-ids allocated
by the plugin, and NOT the host, which I like more.
Having the plugins allocate them is a pain, its much easier if the host
aloocates them, and just does so from a sufficiently large pool, if you
have 2^32 host VVIDs per instrument you can just round robin them.
4:17 p.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Wednesday 08 January 2003 08.37, Tim Hockin wrote:
Why is it a pain? I think it is clean. I've never cared for the
idea of Virtual Voices. Either a voice is on, or it is not. The
plugin and the host need to agree on that.
I simply don't see why. This is tracker philosophy. MIDI sequencers
never have a clue about what synths are actually doing, but it all
works just fine anyway. (Better than traditional trackers ever could,
for most things, I'd say.)
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
--- http://olofson.net --- http://www.reologica.se ---
Either you need to NEVER re-use a VVID, or you need to
tell the
host when an ended VVID is actually re-usable. Or you need to
have voice-ids allocated by the plugin, and NOT the host, which
I like more.
Having the plugins allocate them is a pain, its much easier if
the host aloocates them, and just does so from a sufficiently
large pool, if you have 2^32 host VVIDs per instrument you can
just round robin them.
7 Jan
7 Jan
8:31 a.m.
New subject: [linux-audio-dev] more on XAP Virtual Voice ID system
On Tuesday 07 January 2003 09.15, Tim Hockin wrote:
Or you can tell the plugin when you want a particular VVID to be
assigned to a new voice.
[...]
I'm actually arguing that *no* specific event or control is the "note
on". It could be triggered by VELOCITY changes, or by any other Voice
Control or combination of Voice Controls. It's entirely synth
specific.
Well, it's not quite that simple with continous velocity
instruments... You may want to steal a voice when the velocity is
high enough, and possibly even have some other "context" steal it
back later on. (It would be the right thing to do - but if someone
actually cares to implement it is another matter. It is, after all,
little more than an emergency solution.)
Yeah, it's basically a mattor of allocation - either of a physical
voice, or a temporary "fake voice" or something else that can track
the incoming events until a physical voice is allocated.
I think different synths will want to do this in different ways, but
we need to come up with an API that's clean and works well for all
sensible methods.
Either tell the host/sender when the VVID is free (which means you
need a VVID reserve that has some sort of hard to define relation to
latency), or let the host/sender tell the synth when it no longer
cares about a specific "voice context". I strongly prefer the latter.
The problem is that voice IDs still cannot have a direct relation to
voices. If they have, you can't steal voices, since that would result
in the host/sender sending events for multiple voices using the same
ID. So, this effectively just forces the complexities of "voice
management by reference" into *both* synths and hosts/senders.
Either way, VVID allocation and voice allocation are still two
different issues. VVID is about allocating *references*, while voice
allocation is about actual voices and/or temporary voice control
storage.
//David Olofson - Programmer, Composer, Open Source Advocate
.- The Return of Audiality! --------------------------------.
| Free/Open Source Audio Engine for use in Games or Studio. |
| RT and off-line synth. Scripting. Sample accurate timing. |
`---------------------------> http://olofson.net/audiality -'
--- http://olofson.net --- http://www.reologica.se ---
continuous
note on a particular VVID. The sequencer only reuses a
VVID once it has ended any previous notes on that VVID. The
sequencer can allocate a
This is the current issue at hand - just because the sequencer has
ended a VVID with a voice-off, doesn't mean the voice is off. It
just begins the release phase of the envelope, on some synths.
This could take a while. Either you need to NEVER re-use a VVID, or
you need to tell the host when an ended VVID is actually re-usable.
Or you need to have voice-ids allocated by the plugin, and NOT the
host, which I like more. -HOWEVER-
there is no rule that a note has any pitch or velocity
or any other particular parameter, it is just that the Voice-On
tells the voice to start making sound and the Voice-Off tells the
voice to stop making sound.
Correct. Though David is half-heartedly arguing that maybe
Velocity is the true note-on. I disagree. -ALSO HOWEVER-
the entity which sends voice-on and off messages
may not directly refer to the object's voices. Instead, the event
sender puts
..in the currently understood VVID model.
voices to do. This differential is in place
because sequencers
typically send more concurrent notes than the plugin has actual
voices for AND the
On the contrary, hopefully you will rarely exceed the max polyphony
for each instrument.
other words, it is the role of the plugin to
decide whether or
not to steal
I believe you should always steal notes, but I suppose there will
be some instrument plugin some lunatic on here will devise that
does not follow that. Newer notes are always more important than
older notes, but if you exceed max poly, a red light should go off!
Yes! Bad things *will* happen in 99% of cases. (Whether you can
actually hear the difference in a full mix is another matter.)
(1)send
voice-on event at timestamp X. This indicates a note is
to start.
(2)send parameter-set events also at timestamp X, these are
guaranteed to
This is also for debate - David dislikes (and I agree) the notion
that you have to send a note-on but the plugin does not have enough
info to handle (for example) a velocity-mapped sampler until later.
Process events in order. So a few ideas are on the table. (4)send
voice-off event at later time to end the note and free
the voice.
And what of step-sequencing, where you send a note-on and never a
note-off? Finite duration voices (samples, drum hits, etc) end
spontaneously. Does the plugin tell the host about it, or just let
the VVID leak? When the
plugin reads the voice-on event at timestamp X it
decides whether to allocate a voice or not. If it has an
initialization routine for voice-on events, then the plugin must
read through the remaining events with timestamp X to get
initialization arguments. The plugin must delay actually
I guess it may not be tooo bad. Plugins which need some init info
(such as velocity for the velo-map) know they need this, and can
look for that info. Other plugins for whom an init event is no
different than a continuous event just go about their merry way.
But before we all decide this, I want to explore other notions.
I'm not saying my negative Voice-ID thing is great, but I rather
like the idea that Voice-Ids mean something and are almost purely
the domain of the plugin.
7926
days inactive
7927
days old
linux-audio-dev@lists.linuxaudio.org
13 comments
5 participants
participants (5)
-
David Olofson -
Kjetil S. Matheussen -
robbins jacob -
Steve Harris -
Tim Hockin