singe/singe/videoPlayer.c

/*
 *
 *  Singe 2
 *  Copyright (C) 2006-2020 Scott Duensing <scott@kangaroopunch.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */


#include <SDL2/SDL_mixer.h>
#include <ffms.h>

#include "thirdparty/uthash.h"

#include "util.h"
#include "videoPlayer.h"


#define AUDIO_STREAM_LOW_WATERMARK  (24 * 1024)
#define AUDIO_SAMPLE_PREREAD        1024
#define AUDIO_SILENCE_SECONDS       2


#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpadded"
typedef struct VideoPlayerS {
		int32_t                     id;
		bool                        playing;
		bool                        resetTime;
		byte                       *audioBuffer;
		byte                        audioSampleBytes;
		byte                       *audioSilenceRaw;
		char                        errMsg[1024];
		int32_t                     volumeLeft;
		int32_t                     volumeRight;
		int32_t                     audioTrack;
		int32_t                     videoTrack;
		int32_t                     audioSampleSize;
		int32_t                     mixSampleSize;
		int32_t                     audioSilenceChannel;
		int64_t                     frame;
		int64_t                     audioBufferSize;
		int64_t                     frameDeltaTime;
		int64_t                     lastFrameTime;
		int64_t                     timestamp;
		int64_t                     audioDelta;
		int64_t                     audioPosition;
		int64_t                     framesPlayed;
		Uint16                      audioFormat;
		Uint32                      lastTickTime;
		Uint32                      audioSilenceSize;
		double                      audioAdjustment;
		Mix_Chunk                  *silenceChunk;
		SDL_AudioStream            *audioStream;
		SDL_Texture                *videoTexture;
		FFMS_ErrorInfo              errInfo;
		FFMS_AudioSource           *audioSource;
		FFMS_VideoSource           *videoSource;
		const FFMS_AudioProperties *audioProps;
		const FFMS_VideoProperties *videoProps;
		const FFMS_Frame           *propFrame;
		const FFMS_TrackTimeBase   *videoTimeBase;
		const FFMS_Frame           *frameData;
		const FFMS_FrameInfo       *frameInfo;
		UT_hash_handle              hh;
} VideoPlayerT;
#pragma GCC diagnostic pop


FFMS_Index  *_createIndex(char *filename, char *indexPath, bool hasVideo, bool hasAudio, VideoPlayerT *v);
void         _dequeueVideoAudio(int channel, void *stream, int len, void *udata);  // Callback.  Not changing ints.
int FFMS_CC  _indexCallBack(int64_t Current, int64_t Total, void *ICPrivate);      // Callback.  Not changing int.
int32_t      _loadVideoAndAudio(char *vFilename, char *aFilename, char *indexPath, bool stretchVideo, SDL_Renderer *renderer);


static VideoPlayerT    *_videoPlayerHash =  NULL;
static int32_t          _nextId          =  0;
static int32_t          _mixRate         = -1;
static Uint8            _mixChannels     =  0;
static SDL_AudioFormat  _mixFormat       =  0;


void _dequeueVideoAudio(int channel, void *stream, int bytes, void *udata) {   // Callback.  Not changing ints.
	VideoPlayerT *v             = (VideoPlayerT *)udata;
	int32_t       bytesToCopy   = bytes;
	int32_t       available     = SDL_AudioStreamAvailable(v->audioStream);
	int32_t       remainder     = 0;
	int32_t       bytesRead     = 0;
	int32_t       i             = 0;
	Sint16       *data          = stream;

	(void)channel;

	// Don't copy more than we have room for
	if (bytesToCopy > available) {
		bytesToCopy = available;
	}

	// Ensure we only copy complete samples (Is this needed?)
	remainder = bytesToCopy % v->audioSampleSize;
	bytesToCopy -= remainder;

	//utilSay("B: %d  R: %d  W: %ld", bytes, remainder, SDL_AudioStreamAvailable(v->audioStream));

	// Read audio data
	bytesRead = SDL_AudioStreamGet(v->audioStream, stream, bytesToCopy);
	if (bytesRead < 0) utilDie("%s", SDL_GetError());

	// We do our own volume per channel here in the mixer
	if (_mixChannels < 2) {
		// Mono output, average volume levels together
		Mix_Volume(channel, (int32_t)((float)MIX_MAX_VOLUME * ((float)v->volumeLeft * (float)v->volumeRight / (float)2) * (float)0.01));
	} else {
		// Stereo output.  Assumes MIX_DEFAULT_FORMAT for now.
		Mix_Volume(channel, MIX_MAX_VOLUME);
		for (i=0; i<bytesRead / 2; i+=2) {
			data[i] = (Sint16)((float)data[i] * (float)v->volumeLeft * (float)0.01);
			data[i + 1] = (Sint16)((float)data[i + 1] * (float)v->volumeRight * (float)0.01);
		}
	}
}


int FFMS_CC _indexCallBack(int64_t current, int64_t total, void *ICPrivate) {   // Callback.  Not changing int.
	static int32_t lastPercent = 0;
	int32_t        thisPercent = 0;

	(void)ICPrivate;  // Contains current VideoPlayerT

	if ((current == 0) && (total == 0)) {
		lastPercent = 0;  // Reset
	} else {
		thisPercent = (int32_t)((double)current / (double)total * 100.0);
		if (thisPercent != lastPercent) {
			lastPercent = thisPercent;
			utilSay("Indexing:  %d%%", thisPercent);
			//***TODO*** GUI
		}
	}

	return 0;
}


FFMS_Index *_createIndex(char *filename, char *indexPath, bool hasVideo, bool hasAudio, VideoPlayerT *v) {
	char             indexName[1024];
	FFMS_Index      *index           =  NULL;
	FFMS_Indexer    *indexer         =  NULL;

	// Index file
	snprintf(indexName, 1024, "%s%c%s.index", indexPath, utilGetPathSeparator(), utilGetLastPathComponent(filename));
	index = FFMS_ReadIndex(indexName, &v->errInfo);
	if (index) {
		if (FFMS_IndexBelongsToFile(index, filename, &v->errInfo)) {
			FFMS_DestroyIndex(index);
			index = NULL;
		}
	}
	if (!index) {
		utilSay("Creating new index.");
		indexer = FFMS_CreateIndexer(filename, &v->errInfo);
		if (indexer == NULL) utilDie("%s", v->errInfo.Buffer);
		if (hasAudio) FFMS_TrackTypeIndexSettings(indexer, FFMS_TYPE_AUDIO, 1, 0);
		if (hasVideo) FFMS_TrackTypeIndexSettings(indexer, FFMS_TYPE_VIDEO, 1, 0);
		_indexCallBack(0, 0, v);
		FFMS_SetProgressCallback(indexer, _indexCallBack, v);
		index = FFMS_DoIndexing2(indexer, FFMS_IEH_ABORT, &v->errInfo);
		if (index == NULL) utilDie("%s", v->errInfo.Buffer);
		if (FFMS_WriteIndex(indexName, index, &v->errInfo)) utilDie("%s", v->errInfo.Buffer);
	}

	return index;
}


int32_t _loadVideoAndAudio(char *vFilename, char *aFilename, char *indexPath, bool stretchVideo, SDL_Renderer *renderer) {
	int32_t          pixelFormats[2];
	int32_t          result          = -1;
	FFMS_Index      *vIndex          =  NULL;
	FFMS_Index      *aIndex          =  NULL;
	VideoPlayerT    *v               =  NULL;

	// Create new videoPlayer
	v = calloc(1, sizeof(VideoPlayerT));
	if (!v) utilDie("Unable to allocate new video player.");

	// Set some starting values
	v->audioTrack          = -1;
	v->videoTrack          = -1;
	v->audioSilenceChannel = -1;
	v->playing             = false;  //  Start paused
	v->errInfo.Buffer      = v->errMsg;
	v->errInfo.BufferSize  = sizeof(v->errMsg);
	v->errInfo.ErrorType   = FFMS_ERROR_SUCCESS;
	v->errInfo.SubType     = FFMS_ERROR_SUCCESS;

	if (aFilename) {
		vIndex = _createIndex(vFilename, indexPath, true, false, v);
		aIndex = _createIndex(aFilename, indexPath, false, true, v);
	} else {
		vIndex = _createIndex(vFilename, indexPath, true, true, v);
		aIndex = vIndex;
		aFilename = vFilename;
	}

	// Find video track
	v->videoTrack = FFMS_GetFirstTrackOfType(vIndex, FFMS_TYPE_VIDEO, &v->errInfo);
	if (v->videoTrack < 0) utilDie("%s", v->errInfo.Buffer);
	v->videoSource = FFMS_CreateVideoSource(vFilename, v->videoTrack, vIndex, 1, FFMS_SEEK_NORMAL, &v->errInfo);
	if (v->videoSource == NULL) utilDie("%s", v->errInfo.Buffer);

	// Get video properties
	v->videoProps = FFMS_GetVideoProperties(v->videoSource);
	v->propFrame = FFMS_GetFrame(v->videoSource, 0, &v->errInfo);
	if (v->propFrame == NULL) utilDie("%s", v->errInfo.Buffer);
	v->videoTimeBase = FFMS_GetTimeBase(FFMS_GetTrackFromVideo(v->videoSource));

	// Set up output video format
	pixelFormats[0] = FFMS_GetPixFmt("bgra");
	pixelFormats[1] = -1;
	if (FFMS_SetOutputFormatV2(v->videoSource, pixelFormats, v->propFrame->EncodedWidth, v->propFrame->EncodedHeight, FFMS_RESIZER_BICUBIC, &v->errInfo)) utilDie("%s", v->errInfo.Buffer);

	// Find audio track
	v->audioTrack = FFMS_GetFirstTrackOfType(aIndex, FFMS_TYPE_AUDIO, &v->errInfo);
	if (v->audioTrack < 0) utilDie("%s", v->errInfo.Buffer);
	v->audioSource = FFMS_CreateAudioSource(aFilename, v->audioTrack, aIndex, FFMS_DELAY_FIRST_VIDEO_TRACK, &v->errInfo);
	if (v->audioSource == NULL) utilDie("%s", v->errInfo.Buffer);

	// Get audio properties
	v->audioProps = FFMS_GetAudioProperties(v->audioSource);

	// Indicies are now part of audioSource & videoSource, so release these
	FFMS_DestroyIndex(vIndex);
	vIndex = NULL;
	if (aFilename != vFilename) {
		FFMS_DestroyIndex(aIndex);
	}
	aIndex = NULL;

	// Create video texture
	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "linear");
	v->videoTexture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_BGRA32, SDL_TEXTUREACCESS_TARGET, v->propFrame->EncodedWidth, v->propFrame->EncodedHeight);
	if (v->videoTexture == NULL) utilDie("%s", SDL_GetError());
	if (!stretchVideo) {
		SDL_RenderSetLogicalSize(renderer, v->propFrame->EncodedWidth, v->propFrame->EncodedHeight);
	}

	// Determine audio format
	switch (v->audioProps->SampleFormat) {
		case FFMS_FMT_U8:
			v->audioFormat = AUDIO_U8;
			v->audioSampleBytes = 1;
			break;
		case FFMS_FMT_S16:
			v->audioFormat = AUDIO_S16SYS;
			v->audioSampleBytes = 2;
			break;
		case FFMS_FMT_S32:
			v->audioFormat = AUDIO_S32SYS;
			v->audioSampleBytes = 4;
			break;
		case FFMS_FMT_FLT:
			v->audioFormat = AUDIO_F32SYS;
			v->audioSampleBytes = 4;
			break;
		default:
			utilDie("Unknown audio sample format.");
			break;
	}
	if (v->audioProps->Channels > 2) utilDie("Only mono and stereo audio are supported.");

	// Create audio stream to convert audio to our desired format
	v->audioStream = SDL_NewAudioStream(v->audioFormat, (Uint8)v->audioProps->Channels, v->audioProps->SampleRate, _mixFormat, _mixChannels, _mixRate);
	if (!v->audioStream) utilDie("%s", SDL_GetError());

	// Create a buffer to read audio into before conversion
	v->mixSampleSize = SDL_AUDIO_BITSIZE(_mixFormat) / 8 * _mixChannels;
	v->audioSampleSize = v->audioSampleBytes * v->audioProps->Channels;
	v->audioBufferSize = v->audioSampleSize * AUDIO_SAMPLE_PREREAD;
	v->audioBuffer = (byte *)malloc((size_t)v->audioBufferSize * sizeof(byte));
	if (!v->audioBuffer) utilDie("Unable to allocate %ld byte audio buffer.", (size_t)v->audioBufferSize * sizeof(byte));

	// Create a block of silent audio to overlay with video stream audio
	v->audioSilenceSize = (Uint32)(_mixRate * SDL_AUDIO_BITSIZE(_mixFormat) / 8 * AUDIO_SILENCE_SECONDS);
	v->audioSilenceRaw = (byte *)calloc(1, (size_t)v->audioSilenceSize * sizeof(byte));
	if (!v->audioSilenceRaw) utilDie("Unable to allocate %ld silence buffer.", v->audioSilenceSize);

	// Load silent audio
	v->silenceChunk = Mix_QuickLoad_RAW(v->audioSilenceRaw, v->audioSilenceSize);
	if (!v->silenceChunk) utilDie("%s", Mix_GetError());

	// Start silent audio playback & immediately pause it
	v->audioSilenceChannel = Mix_PlayChannel(-1, v->silenceChunk, -1);
	if (v->audioSilenceChannel < 0) utilDie("%s", Mix_GetError());

	// Register effect to provide video stream audio on this channel
	Mix_RegisterEffect(v->audioSilenceChannel, _dequeueVideoAudio, NULL, v);

	// Default volume, in percent
	v->volumeLeft  = 100;
	v->volumeRight = 100;

	/*
	utilSay("Frames:  %d  (%dx%d)  Audio Samples:  %ld  (%d Hz)  %d Channel%s",
		v->videoProps->NumFrames,
		v->propFrame->EncodedWidth,
		v->propFrame->EncodedHeight,
		v->audioProps->NumSamples,
		v->audioProps->SampleRate,
		v->audioProps->Channels,
		v->audioProps->Channels == 1 ? "" : "s"
	);
	*/

	// Add to player hash
	v->id = _nextId;
	HASH_ADD_INT(_videoPlayerHash, id, v);
	result = _nextId++;

	return result;
}


int32_t videoInit(void) {

	int32_t channels = _mixChannels;

	// Start FFMS
	FFMS_Init(0, 0);

	// Fetch mixer settings
	if (!Mix_QuerySpec(&_mixRate, &_mixFormat, &channels)) utilDie("%s", Mix_GetError());
	_mixChannels = (Uint8)channels;

	// Volume only works with MIX_DEFAULT_FORMAT
	if (_mixFormat != MIX_DEFAULT_FORMAT) utilDie("videoInit:  Only MIX_DEFAULT_FORMAT audio is supported.");

	return 0;
}


int32_t videoIsPlaying(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoIsPlaying.", playerHandle);

	return v->playing;
}


int64_t videoGetFrame(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoGetFrame.", playerHandle);

	return v->frame;
}


int64_t videoGetFrameCount(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoGetFrameCount.", playerHandle);

	return v->videoProps->NumFrames;

}


int32_t videoGetHeight(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoGetHeight.", playerHandle);

	return v->propFrame->EncodedHeight;
}


int32_t videoGetWidth(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoGetWidth.", playerHandle);

	return v->propFrame->EncodedWidth;
}


int32_t videoGetVolume(int32_t playerHandle, int32_t *leftPercent, int32_t *rightPercent) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoGetVolume.", playerHandle);

	if (leftPercent  != NULL) *leftPercent  = v->volumeLeft;
	if (rightPercent != NULL) *rightPercent = v->volumeRight;

	return 0;
}


int32_t videoLoad(char *filename, char *indexPath, bool stretchVideo, SDL_Renderer *renderer) {
	return _loadVideoAndAudio(filename, NULL, indexPath, stretchVideo, renderer);
}


int32_t videoLoadWithAudio(char *vFilename, char *aFilename, char *indexPath, bool stretchVideo, SDL_Renderer *renderer) {
	return _loadVideoAndAudio(vFilename, aFilename, indexPath, stretchVideo, renderer);
}


int32_t videoPause(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoPause.", playerHandle);

	v->playing   = false;
	v->resetTime = true;

	return 0;
}


int32_t videoPlay(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoPlay.", playerHandle);

	v->playing   = true;
	v->resetTime = true;

	return 0;
}


int32_t videoQuit(void) {

	VideoPlayerT *v = NULL;
	VideoPlayerT *t = NULL;

	// Unload any remaining videos
	HASH_ITER(hh, _videoPlayerHash, v, t) {
		videoUnload(v->id);
	}

	FFMS_Deinit();

	return 0;
}


int32_t videoSeek(int32_t playerHandle, int64_t seekFrame) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoSeek.", playerHandle);

	while (seekFrame >= v->videoProps->NumFrames) {
		seekFrame -= v->videoProps->NumFrames;
	}
	while (seekFrame < 0) {
		seekFrame += v->videoProps->NumFrames;
	}

	v->frame = seekFrame;
	v->resetTime = true;

	return 0;
}


int32_t videoSetVolume(int32_t playerHandle, int32_t leftPercent, int32_t rightPercent) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoSetVolume.", playerHandle);

	v->volumeLeft  = leftPercent;
	v->volumeRight = rightPercent;

	return 0;
}


int32_t videoUnload(int32_t playerHandle) {
	VideoPlayerT *v = NULL;

	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoStop.", playerHandle);

	Mix_HaltChannel(v->audioSilenceChannel);
	Mix_UnregisterEffect(v->audioSilenceChannel, _dequeueVideoAudio);
	Mix_FreeChunk(v->silenceChunk);
	free(v->audioSilenceRaw);
	SDL_FreeAudioStream(v->audioStream);
	free(v->audioBuffer);

	FFMS_DestroyAudioSource(v->audioSource);
	FFMS_DestroyVideoSource(v->videoSource);

	SDL_DestroyTexture(v->videoTexture);

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
	HASH_DEL(_videoPlayerHash, v);
#pragma GCC diagnostic pop
	free(v);

	return 0;
}


int32_t videoUpdate(int32_t playerHandle, SDL_Texture **texture) {
	int32_t       result     = -1;
	int64_t       count      =  0;
	int64_t       threshold  =  0;
	VideoPlayerT *v          =  NULL;


	// Get our player structure
	HASH_FIND_INT(_videoPlayerHash, &playerHandle, v);
	if (!v) utilDie("No video player at index %d in videoUpdate.", playerHandle);

	// Audio drift limit
	threshold = (v->audioProps->SampleRate / 2);

	// Handle video frames (and time)
	if ((SDL_GetTicks() - v->lastTickTime >= v->frameDeltaTime) || (v->audioDelta > threshold) || v->resetTime) {

		v->lastTickTime = SDL_GetTicks();

		if (v->frameData) {
			SDL_UpdateTexture(v->videoTexture, NULL, v->frameData->Data[0], v->frameData->Linesize[0]);
		}

		*texture = v->videoTexture;
		result  = v->frame;
		v->framesPlayed++;

		// Did we trip the audio sync compensation?
		if (v->audioDelta > threshold) {
			// Adjust frame rate to try and match
			if (v->audioDelta > 0) {
				v->audioAdjustment += 0.000001;
			} else {
				v->audioAdjustment -= 0.000001;
			}
		}

		// Used to determine if we should play two frames rapidly to catch up to audio
		v->audioDelta = labs(v->audioPosition - (int64_t)((double)v->timestamp * 0.001 * (double)v->audioProps->SampleRate));

		utilSay("D %ld  T %ld  A %f", v->audioDelta, threshold, v->audioAdjustment);

		v->frameData = FFMS_GetFrame(v->videoSource, v->frame, &v->errInfo);
		if (v->frameData == NULL) utilDie("%s", v->errInfo.Buffer);
		v->frameInfo = FFMS_GetFrameInfo(FFMS_GetTrackFromVideo(v->videoSource), v->frame);
		v->timestamp = (int64_t)((double)v->frameInfo->PTS * (double)v->videoTimeBase->Num / (double)v->videoTimeBase->Den);  // Convert to milliseconds
		v->frameDeltaTime = (v->timestamp - v->lastFrameTime); // - (v->audioAdjustment * v->framesPlayed);
		v->lastFrameTime = v->timestamp;

		if (v->playing) {
			if (++v->frame >= v->videoProps->NumFrames) {
				v->frame = 0;
				v->timestamp = 0;
				v->resetTime = true;
			}
		}

		if (v->resetTime)  {
			SDL_AudioStreamClear(v->audioStream);
			v->lastTickTime = 0;
			v->frameDeltaTime = 0;
			v->audioPosition = (int64_t)((double)v->timestamp * 0.001 * (double)v->audioProps->SampleRate);
			v->resetTime = false;
			v->audioDelta = 0;
			v->framesPlayed = 0;
		}
	}

	// Handle audio samples
	if ((v->playing) && (SDL_AudioStreamAvailable(v->audioStream) < AUDIO_STREAM_LOW_WATERMARK) && (v->audioPosition < v->audioProps->NumSamples)) {
		// Maximum samples we can read at a time
		count = AUDIO_SAMPLE_PREREAD;
		// Don't read past end of audio data
		if (v->audioPosition + count >= v->audioProps->NumSamples) {
			count = v->audioProps->NumSamples - v->audioPosition - 1;
		}
		// Are we reading anything?
		if (count > 0) {
			// Get audio from video stream
			if (FFMS_GetAudio(v->audioSource, v->audioBuffer, v->audioPosition, count, &v->errInfo)) utilDie("%s", v->errInfo.Buffer);
			// Feed it to the mixer stream
			if (SDL_AudioStreamPut(v->audioStream, v->audioBuffer, (int32_t)(count * v->audioSampleSize)) < 0) utilDie("%s", SDL_GetError());
			v->audioPosition += count;
		}
	}

	return result;
}