Function Vorbis_DecodeFrame

src/Vorbis.c:1446–1587

#######################################################################################################################* *-----------------------------------------------------Vorbis frame--------------------------------------------------------* *#########################################################################################################################*/ Vorbis spec 4.3. Audio packe

*#########################################################################################################################*/
/* Vorbis spec 4.3. Audio packet decode and synthesis */
cc_result Vorbis_DecodeFrame(struct VorbisState* ctx) {
	/* frame header */
	cc_uint32 packetType;
	struct Mapping* mapping;
	struct Mode* mode;
	int modeIdx;

	/* floor/residue */
	cc_bool hasFloor[VORBIS_MAX_CHANS];
	cc_bool hasResidue[VORBIS_MAX_CHANS];
	cc_bool doNotDecode[VORBIS_MAX_CHANS];
	float* data[VORBIS_MAX_CHANS];
	int submap, floorIdx;
	int ch, residueIdx;

	/* inverse coupling */
	int magChannel, angChannel;
	float* magValues, m;
	float* angValues, a;

	/* misc variables */
	float* tmp;
	cc_uint32 alignSkip;
	int i, j; 
	cc_result res;
	
	res = Vorbis_TryReadBits(ctx, 1, &packetType);
	if (res) return res;
	if (packetType) return VORBIS_ERR_FRAME_TYPE;

	modeIdx = Vorbis_ReadBits(ctx, ctx->modeNumBits);
	mode    = &ctx->modes[modeIdx];
	mapping = &ctx->mappings[mode->mappingIdx];

	/* decode window shape */
	ctx->curBlockSize = ctx->blockSizes[mode->blockSizeFlag];
	ctx->dataSize     = ctx->curBlockSize / 2;
	/* long window lapping flags - we don't care about them though */
	if (mode->blockSizeFlag) { Vorbis_ReadBits(ctx, 2); } /* TODO: do we just SkipBits here */

	/* swap prev and cur outputs around */
	tmp = ctx->values[1]; ctx->values[1] = ctx->values[0]; ctx->values[0] = tmp;
	Mem_Set(ctx->values[0], 0, ctx->channels * ctx->curBlockSize);

	for (i = 0; i < ctx->channels; i++) 
	{
		ctx->curOutput[i]  = ctx->values[0] + i * ctx->curBlockSize;
		ctx->prevOutput[i] = ctx->values[1] + i * ctx->prevBlockSize;
	}

	/* decode floor */
	for (i = 0; i < ctx->channels; i++) 
	{
		submap   = mapping->mux[i];
		floorIdx = mapping->floorIdx[submap];
		hasFloor[i]   = Floor_DecodeFrame(ctx, &ctx->floors[floorIdx], i);
		hasResidue[i] = hasFloor[i];
	}