How to Destroy a Libopus Encoder to Free Memory

Proper memory management is critical when integrating the Opus audio codec into your applications to prevent resource leaks. This article explains the correct procedure for destroying an OpusEncoder state and freeing its allocated memory in libopus, addressing both standard heap allocation and custom memory management workflows.

Standard Deallocation with opus_encoder_destroy

If you allocated the encoder state dynamically using the standard opus_encoder_create function, you must use the corresponding opus_encoder_destroy function to deallocate it.

The opus_encoder_create function allocates memory internally on the heap. Calling opus_encoder_destroy safely releases this memory back to the system.

#include <opus.h>

// 1. Create the encoder
int error;
OpusEncoder *encoder = opus_encoder_create(48000, 2, OPUS_APPLICATION_AUDIO, &error);

if (error == OPUS_OK) {
    // Use the encoder...
    
    // 2. Properly destroy the encoder and free memory
    opus_encoder_destroy(encoder);
    encoder = NULL; // Prevent dangling pointer
}

Passing a NULL pointer to opus_encoder_destroy is safe and will result in a no-op, but it is best practice to set the pointer to NULL after destruction to avoid double-free errors.

Deallocation with Custom Memory Management

If your application manages memory manually to avoid heap fragmentation, you may have used opus_encoder_get_size to determine the state size and opus_encoder_init to initialize a pre-allocated block of memory.

In this scenario, opus_encoder_destroy should not be used. Because libopus did not allocate the memory, you must free the memory block using the same mechanism you used to allocate it (such as standard free() or a custom pool allocator).

#include <stdlib.h>
#include <opus.h>

// 1. Get size and allocate memory manually
int size = opus_encoder_get_size(2); // 2 channels
OpusEncoder *encoder = (OpusEncoder *)malloc(size);

if (encoder != NULL) {
    // 2. Initialize the encoder
    int error = opus_encoder_init(encoder, 48000, 2, OPUS_APPLICATION_AUDIO);
    
    if (error == OPUS_OK) {
        // Use the encoder...
    }
    
    // 3. Free the memory manually (do not use opus_encoder_destroy)
    free(encoder);
    encoder = NULL;
}

By matching the destruction method to your allocation method, you ensure that your application remains free of memory leaks when using libopus.