OpenAL 1.1 AL_MAX_DISTANCE boundary and source count limits

Answer

AL_MAX_DISTANCE does not guarantee that a source becomes inaudible, and the maximum number of simultaneous sources is not portable across OpenAL implementations.

Confirmed facts

• The OpenAL 1.1 specification defines AL_MAX_DISTANCE as the distance beyond which attenuation stops increasing; it does not force the gain to zero.
• Audibility at distances ≥ AL_MAX_DISTANCE depends on the active distance model. With clamped models (e.g., AL_INVERSE_DISTANCE_CLAMPED) the gain is fixed to the value computed at AL_MAX_DISTANCE; with unclamped models the gain continues to follow the model’s formula.
• The maximum number of hardware or software sources is implementation‑defined. OpenAL Soft is limited mainly by available memory and CPU, while proprietary drivers are often limited by a fixed number of hardware voices (commonly 32‑64).
• When the source limit is exceeded, most implementations return AL_OUT_OF_MEMORY from alGenSources, but the spec does not require a specific error code; some drivers may return AL_INVALID_VALUE or no error at all.

Likely explanation

Because attenuation stops increasing at AL_MAX_DISTANCE, a source will only be silent if the chosen distance model yields zero gain at that distance (or if the application explicitly sets the gain to zero). Otherwise the source remains audible at a constant, low level. Similarly, source‑count limits vary: OpenAL Soft can create many more sources than a vendor driver that exposes a fixed hardware voice count, so code that assumes a universal limit will fail on some platforms.

Steps to verify on your system

1. Query the current distance model: alGetListenerf(AL_DISTANCE_MODEL, &model).
2. Create a source, set its position to a distance > AL_MAX_DISTANCE, and check its gain: alGetSourcef(source, AL_GAIN, &gain). If the gain equals the value computed at AL_MAX_DISTANCE (for a clamped model) or follows the model’s formula (for an unclamped model), you have confirmed the behavior.
3. To find the practical source limit, repeatedly call alGenSources(1, &src) in a loop until the function returns AL_FALSE or alGetError() returns a non‑zero value. Count the successful generations.

Missing diagnostic detail

To give a precise recommendation about inaudibility, please specify which distance model you are using (or whether you plan to set the gain manually). This determines whether AL_MAX_DISTANCE will produce silence or a constant low level.