Re: Code to create UIImage of waveform from audiofile?
Re: Code to create UIImage of waveform from audiofile?
- Subject: Re: Code to create UIImage of waveform from audiofile?
- From: Thomas Thiriez <email@hidden>
- Date: Sat, 20 Mar 2010 12:22:57 +0100
On Mar 20, 2010, at 4:22 AM, Paul Davis wrote:
> On Fri, Mar 19, 2010 at 10:53 PM, David Duncan <email@hidden> wrote:
>> On Mar 19, 2010, at 5:30 PM, Tom Blench wrote:
>>
>> Not that I know of. Not too difficult to write yourself though.
>> Subsampling and taking the absolute value of the wave should work.
>>
>> If your up for it, you might consider using the audio converter do the
>> re-sampling for you. You can also let Quartz do the scaling for you, so you
>> should barely need to touch the values from the wave form yourself.
>
> all of this depends a great deal on what you want to do with the
> "image" and how much efficiency counts. we have 2 highly tweaked
> waveform display implementations for ardour, one built on standard
> (cross-platform) APIs and the other built on blitting into an RGBA
> buffer. we've been unable to get the standard API based one closer
> than 90% of the speed of the truly custom one. for some purposes, this
> sort of thing doesn't matter.
>
> --p
In my experience, the API used for drawing the waveform is not the
most important thing. You are just drawing a bunch of vertical lines.
What is important is the data structure you use to keep the waveform
in memory so that you can redraw it without having to read the whole
file from disk every time.
Thomas
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