Comments (14)
It depends on how exactly you get the audio. If it's just a continuous stream, as I suspect VoIP generally is, a custom decoder would make more sense, whereas an IO factory is basically for handling a virtual or non-standard file system interface.
With an IO factory, it needs to generate "file" handles that contain set data; it would need to have appropriate format headers in the appropriate places and be able to seek to skip over or read the same data multiple times. A custom decoder, on the other hand, only needs functions that report information about the audio (its format, etc), and a function to provide audio samples in the reported format.
A decoder can "run" pretty much endlessly as long as it can keep providing more samples on request, whereas a file from an IO factory needs to have static data like a file on disk would.
from alure.
Create and use a custom decoder, like this:
class MyDecoder : public alure::Decoder {
uint64_t mPos{0u};
ALfloat mSineFrequency{0.0f};
public:
MyDecoder(ALfloat freq) : mFrequency(freq) { }
ALuint getFrequency() const noexcept override
{
/* Sample rate of the buffer or stream, not your sine wave. Could use the
* device's native sample rate instead. */
return 44100;
}
ChannelConfig getChannelConfig() const noexcept override
{
/* Mono if you want to position it in 3D, or you don't need stereo. */
return alure::ChannelConfig::Mono;
};
SampleType getSampleType() const noexcept override
{
/* Int16 might be more compatible, but Float32 is usually easier for
* synthesized audio. */
return alure::SampleType::Float32;
}
/* This returns the total number of sample frames you want the buffer
* or stream to be. If this returns 0, it can't be used for a plain buffer,
* but can be used for an unending stream that constantly generates
* new samples as it plays. */
uint64_t getLength() const noexcept override { return ...; }
/* Not applicable to a buffer, or non-seekable stream. */
bool seek(uint64_t pos) noexcept override { return false; }
/* Don't need to bother with this if you don't need special loop points. */
std::pair<uint64_t,uint64_t> getLoopPoints() const noexcept override
{ return std::make_pair<uint64_t,uint64_t>(0u, 0u); }
/* This writes the actual buffer data. Assuming you're starting from the "mPos"
* sample position, write "count" samples to "ptr". Use "mSineFrequency" and
* the buffer/stream sample rate reported above as needed. It won't ask for
* more samples in total than the previously-specified length, if it was non-0. */
ALuint read(ALvoid *ptr, ALuint count) noexcept override
{
auto dst = static_cast<ALfloat*>(ptr);
/* Write to dst[0...count-1] for mono, [0...count*2 - 1] for stereo, etc. */
/* Increment the current position in case it's called again for another
* chunk, return how much was written. If this returns less than the
* originally requested amount, the buffer or stream ends here. */
mPos += count;
return count;
}
};
Then simply create the buffer once with the context, giving it the custom decoder with the desired frequency:
alure::Buffer MySineBuffer = context->createBufferFrom("my_sine_wave0",
alure::MakeShared<MyDecoder>(MySineFreq));
then hold onto the buffer and use it like normal:
source->play(MySineBuffer);
If you want a different buffer with a different sine frequency, create a different one:
alure::Buffer MyOtherSineBuffer = context->createBufferFrom("my_sine_wave1",
alure::MakeShared<MyDecoder>(MyOtherSineFreq));
[...]
source->play(MyOtherSineBuffer);
Or alternatively, give the decoder directly to a source to stream it without a cached buffer:
source->play(alure::MakeShared<MyDecoder>(MySineFreq), ...);
If you have any difficulty or questions, please ask.
from alure.
from alure.
So, if I take your class model, and modify it to suit my needs, it might become something like (taking from your altonegen.c example and attempting to port it over):
Close. I left a typo in the constructor (sorry about that), so it should be:
SineWaveDecoder(ALfloat freq) : mSineFrequency(freq) { }
The fill loop should also account for mPos
, and fill the whole buffer:
for (ALuint i = 0; i < count; i++)
data[i] += (ALfloat)(std::sin((mPos+i)/smps_per_cycle * 2.0*M_PI) * 1.0);
from alure.
Hi, I have the similar issue that I need to fill a buffer with data. All I have is an id number that corresponds to each of my own songs/sounds in memory. It seems that this relies on me having a file or making my own decoder. I know my data needs to be decoded either as a mp3 or it is a wav though. I thought of replacing FileIOFactory but I haven't been able to get it to work properly so far.
from alure.
All I have is an id number that corresponds to each of my own songs/sounds in memory.
Do you mean you only have pointers to loaded audio files in memory?
from alure.
no I have char* for each id and I also know their length in bytes.
from alure.
I assume that the char
memory is of the audios, that's what I meant by having them loaded. FileIOFactory
as you mentioned is a more logical approach for this, what have you tried so far? If we're going in that direction, we might need a separate issue though, and please post your current code there.
from alure.
moved to issue #41
from alure.
Hi, I have the similar issue that I need to fill a buffer with data. All I have is an id number that corresponds to each of my own songs/sounds in memory. It seems that this relies on me having a file or making my own decoder. I know my data needs to be decoded either as a mp3 or it is a wav though. I thought of replacing FileIOFactory but I haven't been able to get it to work properly so far.
If the audio's already decoded in memory, making a decoder like the above would work. Just instead of supplying a sine frequency and generating the sine wave in the read method, you supply a pointer to the memory, its length, and the audio format, then copy the data from that pointer in the read method. You would only replace the FileIOFactory if you want to use different I/O methods than the standard file functions (for instance if you want to do I/O through PhysFS or your own custom VFS), which isn't what you're doing here.
from alure.
First of all thanks for answering :)
The audio is not already decoded in memory. It is undecoded in memory.
from alure.
from alure.
from alure.
To make a custom decoder, inherit from allure::Decoder
and implement the functions. The class definition describes the functions to implement:
https://github.com/kcat/alure/blob/master/include/AL/alure2.h#L1427
In the case of a continuous stream, you'd have something like
class MyStream final : public alure::Decoder {
...your needed data fields here...
public:
MyStream(...your data parameters...)
{
...set up your data fields here...
}
/* Return the format of the samples being given (see the ChannelConfig
* and SampleType enums)
*/
ALuint getFrequency() const noexcept override
{ return stream frequency; }
alure::ChannelConfig getChannelConfig() const noexcept override
{ return channel config; }
alure::SampleType getSampleType() const noexcept override
{ return sample type; }
/* No defined length, no seeking, no looping. */
uint64_t getLength() const noexcept override { return 0; }
bool seek(uint64_t pos) noexcept override { return false; }
std::pair<uint64_t,uint64_t> getLoopPoints() const noexcept override { return {}; }
ALuint read(ALvoid *ptr, ALuint count) noexcept override
{
... get 'count' samples from your audio input, write to ptr...
return number of samples written to ptr;
}
};
Then you create an instance of your custom decoder, and play it on a source:
auto stream = alure::MakeShared<MyStream>(...your data parameters...);
...
source.play(stream, 4096, 3);
from alure.
Related Issues (20)
- Sample offset should be set only after attaching source to buffer? HOT 1
- Capture and real-time support HOT 7
- Golang port/interface? HOT 6
- feature request: direct modification of spatial locations HOT 4
- Invalid Source ID (getSampleOffsetLatency) HOT 7
- Why did the implementation of alure::AttributePair changed from std::pair to struct? HOT 3
- Why couldn't (or shouldn't) buffers clean themselves? HOT 4
- Please add 3D sound example HOT 5
- I am having troubles with include path for OpenAL headers HOT 4
- Is std::out_of_range suitable for out of range floating points? HOT 2
- fill buffer with data not from file but of a known format HOT 6
- How to safely use Context::precacheBuffersAsync? HOT 2
- Alure libraries can't be linked dynamically on Windows HOT 8
- Questions about the project state HOT 2
- Why does Alure have different include files and which files should we use? HOT 2
- set3DSpatialize HOT 10
- kcat.strangesoft.net site is gone HOT 11
- "alure" prefixed functions not declared or defined in this repository HOT 2
- Crash after playing multiple sources simultaneously HOT 1
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from alure.