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Re: Help needed with a sync-problem

From: Peter van der Noord <peterdunord@gmail.com>
Date: Fri, 3 Aug 2012 19:51:20 +0200
Message-ID: <CAL9tNz9jq_xoaT5mhibobutV_Z0KRUcKxqTFc0FmisbS1oU5+Q@mail.gmail.com>
To: Adam Goode <agoode@google.com>
Cc: Chris Wilson <cwilso@google.com>, Jussi Kalliokoski <jussi.kalliokoski@gmail.com>, public-audio@w3.org
Why are they treated differently than the native nodes? Doesn't every node
have an algorithm to fil a certain buffer? The custom ones will take way
longer than the ones run by native code, but they all have to fill a buffer
in a certain order, and wait for others to do that first.

Peter

2012/8/3 Adam Goode <agoode@google.com>

> They must add some lag in some cases. You don't have an instantaneous
> algorithm running inside there.
>
> Perhaps the issue is that latency is introduced only in one part of a
> subgraph? I thought there were some mechanisms for determining the latency
> and/or synchronizing such latency across multiple subgraphs?
>
>
>
>
> On Fri, Aug 3, 2012 at 1:40 PM, Peter van der Noord <peterdunord@gmail.com
> > wrote:
>
>> I agree fully that it won't be what most developers want or need to do,
>> the api will be used for games and site music/effects mostly, but creating
>> custom nodes would be my primary focus. To be honest, the list of native
>> nodes that i wanted to use has thinned out, due to some behaviours and
>> implementations that were not appropriate for what i wanted. That's all
>> fine by itself, but if i can't recreate them myself...
>>
>> I personally don't think "a lot of people won't be using custom nodes
>> anyway" is a good argument for not  implement them correctly. If they add
>> lag, i can't use them.
>>
>>
>> Peter
>>
>>
>> 2012/8/3 Chris Wilson <cwilso@google.com>
>>
>>> How would you empower the JS node/DSP API to fix this?
>>>
>>> I still think, personally, that there's an awful lot of focus on custom
>>> processing in our discussions here.  I haven't felt the need to build a
>>> JSNode yet - the first one I will build is probably a noise gate/expander,
>>> since that's the only thing I can't easily replicate from the nodes already
>>> available.  I'm not really convinced that what most application developers
>>> want to do - NEED to do - is process audio bits themselves directly.
>>>
>>>
>>> On Fri, Aug 3, 2012 at 10:11 AM, Jussi Kalliokoski <
>>> jussi.kalliokoski@gmail.com> wrote:
>>>
>>>> It's a known and major issue all right, but it's not a bug. There's not
>>>> much that can be done about it though, afaict. The processing thread has to
>>>> buffer enough data (the buffer size) from the inputs of the JSNode before
>>>> its callback can be invoked, and next it just sends an event to the JS
>>>> thread to process the buffer. The audio thread, however, can't wait for the
>>>> JS thread to process the buffer but instead plays back the previously
>>>> processed buffer.
>>>>
>>>> This is one of the reasons why I think we should focus on empowering
>>>> the JS node / DSP API. If you want to add any custom processing to the
>>>> graph, you're going to have to adjust the rest of the graph accordingly and
>>>> you'll end up with more latency. This means that if you want to do
>>>> extensive custom processing you'll probably need to work around the graph
>>>> or just go with just the JS and have your own routing which means you're in
>>>> a much more flexible place already anyway. I think the graph serves best as
>>>> an IO abstraction, and that's the part we should focus on.
>>>>
>>>> Cheers,
>>>> Jussi
>>>>
>>>>
>>>> On Fri, Aug 3, 2012 at 4:16 PM, Peter van der Noord <
>>>> peterdunord@gmail.com> wrote:
>>>>
>>>>> Well, it seems indeed that custom-nodes add a delay-time to the
>>>>> signal. I've connected a few bypass modules (they write their input to the
>>>>> output) and i'm magically creating an echo...
>>>>>
>>>>> http://www.petervandernoord.nl/patchwork_js/?patch=2&buffer_size=8192
>>>>>
>>>>> (to hear sound, you have to select the loaded buffer from the pulldown
>>>>> in the buffersource-module)
>>>>>
>>>>> I'm getting somewhat confused and concerned about this, why does this
>>>>> happen and isn't this a major bug/issue?
>>>>>
>>>>> Peter
>>>>>
>>>>>
>>>>>
>>>>> 2012/8/2 Adam Goode <agoode@google.com>
>>>>>
>>>>>> I think you can use playbackTime to determine the absolute a-rate
>>>>>> time of the beginning of the javascript buffer. But last I checked it
>>>>>> wasn't present in webkit.
>>>>>>
>>>>>> You might be able to count samples, assuming you know the node's
>>>>>> noteOn time, to keep track of the a-rate time. But with a short buffer
>>>>>> size, sometimes you can have problems as you've noticed.
>>>>>>
>>>>>>
>>>>>> On Thu, Aug 2, 2012 at 4:47 PM, Peter van der Noord <
>>>>>> peterdunord@gmail.com> wrote:
>>>>>>
>>>>>>> Ermmm.....wait, what? And that is intened behavior?
>>>>>>>
>>>>>>> Peter
>>>>>>>
>>>>>>>
>>>>>>> 2012/8/2 Jussi Kalliokoski <jussi.kalliokoski@gmail.com>
>>>>>>>
>>>>>>>> Hey Peter!
>>>>>>>>
>>>>>>>> I think this is because the JSNode has a delay equivalent to the
>>>>>>>> buffer size, hence if you have parallel graphs that contain a different
>>>>>>>> number of JSNodes, they will arrive to the common destination at a
>>>>>>>> different delay.
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> Jussi
>>>>>>>>
>>>>>>>>
>>>>>>>> On Thu, Aug 2, 2012 at 11:35 PM, Peter van der Noord <
>>>>>>>> peterdunord@gmail.com> wrote:
>>>>>>>>
>>>>>>>>> I'm having a strange problem with some signals at the moment and
>>>>>>>>> i've been staring at it for way too long now, so i thought: why not put it
>>>>>>>>> up here, maybe someone sees what's going on. It's a lenghty story, so if
>>>>>>>>> you want to hang on...i'll try to explain :)
>>>>>>>>>
>>>>>>>>> As you may know, i'm writing a modular synthesizer:
>>>>>>>>>
>>>>>>>>> http://petervandernoord.nl/patchwork_js (maybe clear your cache
>>>>>>>>> if you've been there before)
>>>>>>>>>
>>>>>>>>> If you click the 'json to patch' button, a testpatch will be set.
>>>>>>>>> (Important to know: all custom nodes will be created with the buffer-size
>>>>>>>>> that's selected in the pulldown on the right). The patch contains 3 modules
>>>>>>>>> (in patchwork, a module can contain one or more audionodes, with the
>>>>>>>>> module's in/outputs mapped to certain in/outputs of the containing nodes):
>>>>>>>>>
>>>>>>>>> - The destination, which contains a normal destinationNode
>>>>>>>>> http://localhost/patchworkjs/js/modules/DestinationModule.js
>>>>>>>>>
>>>>>>>>> - a clockmodule. one custom js node
>>>>>>>>> http://localhost/patchworkjs/js/modules/DestinationModule.js
>>>>>>>>>
>>>>>>>>> - a triggersequencer, also one custom node.
>>>>>>>>> http://localhost/patchworkjs/js/modules/TriggerSequencerModule.js(the audioprocess callback is at the bottom)
>>>>>>>>>
>>>>>>>>> What is happening in the patch: the clock sends out single values
>>>>>>>>> of 1s (all other values are 0) on a given interval (set in BPM). The
>>>>>>>>> sequencer checks on every incoming value if that value is >0 AND the
>>>>>>>>> previous one was <=0 (i'll call that a clock-pulse). If that is the case,
>>>>>>>>> its SequencerParameter will proceed to the next step. A sequencer-parameter
>>>>>>>>> (actually it is a LogicSequencerParameter, but that's almost the same - it
>>>>>>>>> has one extra method) can be found here:
>>>>>>>>>
>>>>>>>>> http://localhost/patchworkjs/js/params/SequenceParameter.js
>>>>>>>>>
>>>>>>>>> It's basically just an array filled ith 0s and 1s (you can set a 1
>>>>>>>>> by clicking somewhere on the sequencer), and increases the current position
>>>>>>>>> when it gets a next() command. So, back to the the sequencer module: If it
>>>>>>>>> received a clock-pulse, it proceeds the sequencer. Then, if the (new) value
>>>>>>>>> of the sequencer-parameter is 1, the sequencer will write a 1 in its
>>>>>>>>> outputbuffer as well.
>>>>>>>>>
>>>>>>>>> My issues:
>>>>>>>>> - in the testpatch, both the clockmodule and the seq-module are
>>>>>>>>> connected to the output. if you activate some steps in the sequencer, you
>>>>>>>>> will hear that the clicks do not run in sync. I have no idea why that is,
>>>>>>>>> the stepsequencer writes a 1 in exact the same iteration as it reads the
>>>>>>>>> incoming 1s from the clock. In my opinion, they should run exactly in sync.
>>>>>>>>> - When you change the buffersize (which is for the customnodes)
>>>>>>>>> you will hear that the timedifference between the ticks changes (since
>>>>>>>>> there's no clear, you have to refresh the page, set another buffersize and
>>>>>>>>> click 'json to patch')
>>>>>>>>> - Something else i noticed: when i run just a clock module
>>>>>>>>> connected to the output, with a very low buffersize (256, 512), the clock
>>>>>>>>> seems to run very, very irregular.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> So, my main question: Does anyone have any idea why those two
>>>>>>>>> modules do not run in sync when both connected to the output?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Peter
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
Received on Friday, 3 August 2012 17:51:50 GMT

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