Re: Continuous playback of javascript synthesized consecutive audio buffers causes audio artifacts when no buffer starving occurs.

Provided there are no main thread delays, using a ring buffer like
this plays back smoothly in Gecko if "source.buffer = buffer" is
added after changing the buffer.

However, I didn't get the desired result when I tried this change
in Chromium 33.0.1750.46.

Joe is also correct that start(currentTime) can't be used if you
expect playback to be aligned precisely at currentTime, but
start(currentTime) still starts playback as soon as possible.

On Wed, 30 Oct 2013 03:25:03 +0530, Srikumar K. S. wrote:

> Ah I see. 
>
> We've seen some discussion regarding the modifiability of buffers that have 
> been assigned to source nodes (i.e. the "race condition wars"). This jsfiddle
> (http://jsfiddle.net/gy5AU/) shows code that modifies a single 22050Hz
> buffer periodically to generate a glitch-free (up to setTimeout's jitter) 
> 440Hz sine tone.
>
> This produces a clean tone on my machine unlike the original beep.html
> test case ... but should this work at all?
>
> -Kumar
>
> On 30 Oct, 2013, at 1:38 am, Joseph Berkovitz <joe@noteflight.com> wrote:
>
>> If I'm not mistaken I think the original issue here was sequencing audio
>> buffers whose playback rate was not equal to the AC sample rate, and were
>> thus being up- or down-sampled for playback. In this case one gets aliasing
>> problems at the splice point between successive buffers, and the spec is
>> silent about this sort of thing. These aliasing issues do not arise when the
>> playback rate and the AC sample rate are equal.
>> 
>> I don't think the buffer queue model below would address this (although it's
>> very useful in its own right).
>> 
>> On Oct 29, 2013, at 3:18 PM, Srikumar K. S. <srikumarks@gmail.com> wrote:
>> 
>>>> It would allow for pre-synthesized audio playback in a glitch free manner.
>>>> 
>>> I'm not sure whether this is to address an implementation bug or a spec shortcoming. The concept of a buffer queue can already be expressed using the AudioBufferSourceNode. Whether it works without glitches in current implementations is likely not a spec shortcoming .. unless it is impossible to create such an implementation, which I don't think is the case.
>>> 
>>> For instance, see the buffer_queue model at https://github.com/srikumarks/steller/blob/master/src/models/buffer_queue.js. The example code there asks for a function to be called when the queue runs low, but it can sequence buffers passed to the "enqueue" method. 
>>> 
>>> Reproducing the 440Hz sine tone example here -
>>> 
>>>    var ac = new AudioContext;
>>>    var sh = new org.anclab.steller.Scheduler(ac);
>>>    var q = sh.models.buffer_queue();
>>>    q.connect(ac.destination);
>>>    q.on('low', function () {
>>>        var phase = 0.0, dphase = 2.0 * Math.PI * 440.0 / 44100.0;
>>>        return function (lowEvent, q) {
>>>            var audioBuffer = q.createBuffer(1, 1024);
>>>            var chan = audioBuffer.getChannelData(0);
>>>            var i;
>>>            for (i = 0; i < 1024; ++i) {
>>>                chan[i] = 0.2 * Math.sin(phase);
>>>                phase += dphase;
>>>            }
>>>            q.enqueue(audioBuffer);
>>>        };
>>>    }());
>>>    q.start(ac.currentTime);
>>> 
>>> -Kumar
>>> 
>>> On 30 Oct, 2013, at 12:25 am, Patrick Martin <patrick.martin.r@gmail.com> wrote:
>>> 
>>>> It would allow for pre-synthesized audio playback in a glitch free manner.
>>>> 
>>>> On Oct 20, 2013 10:06 PM, "Robert O'Callahan" <robert@ocallahan.org> wrote:
>>>> On Mon, Oct 21, 2013 at 6:35 AM, Srikumar Karaikudi Subramanian
>>>> <srikumarks@gmail.com> wrote:
>>>> What advantage might such an AudioBufferSequenceNode have over a
>>>> ScriptProcessorNode with a queue processing render function?
>>>> 
>>>> It would probably have the advantage of not being susceptible to small
>>>> amounts of main-thread jank.
>>>> 
>>>> Rob
>>>> -- 
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>>>> atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o Whhei csha iids teoa
>>>> stiheer :p atroa lsyazye,d 'mYaonu,r "sGients uapr,e tfaokreg iyvoeunr, 'm
>>>> aotr atnod sgaoy ,h o'mGee.t" uTph eann dt hwea lmka'n?  gBoutt uIp
>>>> waanndt wyeonut thoo mken.o w
>>> 
>> 
>> .            .       .    .  . ...Joe
>> 
>> Joe Berkovitz
>> President
>> 
>> Noteflight LLC
>> Boston, Mass.
>> phone: +1 978 314 6271
>> www.noteflight.com
>> "Your music, everywhere"
>>

Received on Thursday, 13 February 2014 09:16:14 UTC