Allocates an AVEncryptionInfo structure and sub-pointers to hold the given
number of subsamples. This will allocate pointers for the key ID, IV,
and subsample entries, set the size members, and zero-initialize the rest.
@param subsample_count The number of subsamples.
@param key_id_size The number of bytes in the key ID, should be 16.
@param iv_size The number of bytes in the IV, should be 16.
@return The new AVEncryptionInfo structure, or NULL on error.
Allocates an AVEncryptionInfo structure and sub-pointers to hold the given number of subsamples. This will allocate pointers for the key ID, IV, and subsample entries, set the size members, and zero-initialize the rest.
@param subsample_count The number of subsamples. @param key_id_size The number of bytes in the key ID, should be 16. @param iv_size The number of bytes in the IV, should be 16.
@return The new AVEncryptionInfo structure, or NULL on error.