C & Fmod Ex - playing a PCM array/buffer in Real Time

问题

I use an array to process radio signal and to obtain raw PCM audio. I am desperately trying to play this audio using Fmod Ex.

Basically, would it be possible to create a stream corresponding to my circular buffer, that I could access in a thread-safe way ? Any basic information about what methods to use would be greatly appreciated.

If no, could any other Windows 7 API do the trick and how ? (ASIO, Wasapi...)

Thx °-°

回答1:

I'm assuming your data is continuous (always updating) so you would want to stream it into FMOD, to do this you could override the file callbacks for a particular sound. There is a good example of doing this with the FMOD API usercreatedsound example. If you just want to play a static buffer simply fill out a createsoundexinfo struct describing the data, use the FMOD_OPENMEMORY flag and pass a pointer to the data through createSound as name_or_data. Below is an example of the more complex stream case:

When creating the sound you would use FMOD_CREATESOUNDEXINFO to specify the details of your data, then pass that to createStream. Note this is basically how you would do the static sample case except you are using FMOD_OPENUSER, setting decode size and specifying the callbacks to read the data instead of FMOD_OPENMEMORY and passing the data via the name_or_data param:

FMOD_CREATESOUNDEXINFO exinfo;

memset(&createsoundexinfo, 0, sizeof(FMOD_CREATESOUNDEXINFO));

exinfo.cbsize            = sizeof(FMOD_CREATESOUNDEXINFO);              /* required. */
exinfo.decodebuffersize  = 44100;                                       /* Chunk size of stream update in samples.  This will be the amount of data passed to the user callback. */
exinfo.length            = 44100 * channels * sizeof(signed short) * 5; /* Length of PCM data in bytes of whole song (for Sound::getLength) */
exinfo.numchannels       = channels;                                    /* Number of channels in the sound. */
exinfo.defaultfrequency  = 44100;                                       /* Default playback rate of sound. */
exinfo.format            = FMOD_SOUND_FORMAT_PCM16;                     /* Data format of sound. */
exinfo.pcmreadcallback   = pcmreadcallback;                             /* User callback for reading. */
exinfo.pcmsetposcallback = pcmsetposcallback;                           /* User callback for seeking. */

result = system->createStream(NULL, FMOD_OPENUSER, &exinfo, &sound);
ERRCHECK(result);

Here you are saying that you will provide PCM16 44khz data, customize as required, and give two function callbacks for read and setposition which FMOD will call asking you to either seek your buffer or read something from it:

FMOD_RESULT F_CALLBACK pcmreadcallback(FMOD_SOUND *sound, void *data, unsigned int datalen)
{
    // Read from your buffer here...
    return FMOD_OK;
}


FMOD_RESULT F_CALLBACK pcmsetposcallback(FMOD_SOUND *sound, int subsound, unsigned int position, FMOD_TIMEUNIT postype)
{
    // Seek to a location in your data, may not be required for what you want to do
    return FMOD_OK;
}

That should be everything you need to get FMOD playing back your buffer.

来源：https://stackoverflow.com/questions/4125981/c-fmod-ex-playing-a-pcm-array-buffer-in-real-time