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audio: better docs on conversion APIs, error if not init'd (thanks, Simon!). 

Fixes Bugzilla #3662.
This commit is contained in:
Ryan C. Gordon 2017-08-18 16:52:19 -04:00
parent 500378eb52
commit e3e6b4fd35
2 changed files with 16 additions and 7 deletions
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9
include/SDL_audio.h
View File

@ -450,10 +450,11 @@ extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
* This function takes a source format and rate and a destination format
* and rate, and initializes the \c cvt structure with information needed
* by SDL_ConvertAudio() to convert a buffer of audio data from one format
* to the other.
* to the other. An unsupported format causes an error and -1 will be returned.
* The audio subsystem must be initialized before calling this function.
*
* \return -1 if the format conversion is not supported, 0 if there's
* no conversion needed, or 1 if the audio filter is set up.
* \return 0 if no conversion is needed, 1 if the audio filter is set up,
* or -1 on error.
*/
extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
SDL_AudioFormat src_format,
@ -472,6 +473,8 @@ extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
* The data conversion may expand the size of the audio data, so the buffer
* \c cvt->buf should be allocated after the \c cvt structure is initialized by
* SDL_BuildAudioCVT(), and should be \c cvt->len*cvt->len_mult bytes long.
*
* \return 0 on success or -1 if \c cvt->buf is NULL.
*/
extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);

14
src/audio/SDL_audiocvt.c
View File

@ -22,6 +22,7 @@
/* Functions for audio drivers to perform runtime conversion of audio format */
#include "SDL.h"
#include "SDL_audio.h"
#include "SDL_audio_c.h"
@ -555,7 +556,7 @@ SDL_BuildAudioTypeCVTToFloat(SDL_AudioCVT *cvt, const SDL_AudioFormat src_fmt)
}
if (!filter) {
return SDL_SetError("No conversion available for these formats");
return SDL_SetError("No conversion from source format to float available");
}
if (SDL_AddAudioCVTFilter(cvt, filter) < 0) {
@ -594,7 +595,7 @@ SDL_BuildAudioTypeCVTFromFloat(SDL_AudioCVT *cvt, const SDL_AudioFormat dst_fmt)
}
if (!filter) {
return SDL_SetError("No conversion available for these formats");
return SDL_SetError("No conversion from float to destination format available");
}
if (SDL_AddAudioCVTFilter(cvt, filter) < 0) {
@ -743,8 +744,8 @@ SDL_SupportedChannelCount(const int channels)
/* Creates a set of audio filters to convert from one format to another.
Returns -1 if the format conversion is not supported, 0 if there's
no conversion needed, or 1 if the audio filter is set up.
Returns 0 if no conversion is needed, 1 if the audio filter is set up,
or -1 if an error like invalid parameter, unsupported format, etc. occurred.
*/
int
@ -757,6 +758,11 @@ SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
return SDL_InvalidParamError("cvt");
}
/* Conversions from and to float require the audio subsystem to be initialized */
if (!SDL_WasInit(SDL_INIT_AUDIO)) {
return SDL_SetError("Audio subsystem has not been initialized");
}
/* Make sure we zero out the audio conversion before error checking */
SDL_zerop(cvt);