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add support for downmixing to stereo or mono

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Originally committed as revision 9916 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2007-08-04 22:32:17 +00:00
parent c0d2d806f3
commit 3bbb0bf82c
1 changed files with 111 additions and 14 deletions
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125
libavcodec/ac3dec.c
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@ -76,14 +76,45 @@ static float dynrng_tbl[256];
#define LEVEL_MINUS_3DB 0.7071067811865476
#define LEVEL_MINUS_4POINT5DB 0.5946035575013605
#define LEVEL_MINUS_6DB 0.5000000000000000
#define LEVEL_PLUS_3DB 1.4142135623730951
#define LEVEL_PLUS_6DB 2.0000000000000000
#define LEVEL_MINUS_9DB 0.3535533905932738
#define LEVEL_ZERO 0.0000000000000000
#define LEVEL_ONE 1.0000000000000000
static const float clevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB,
LEVEL_MINUS_6DB, LEVEL_MINUS_4POINT5DB };
static const float gain_levels[6] = {
LEVEL_ZERO,
LEVEL_ONE,
LEVEL_MINUS_3DB,
LEVEL_MINUS_4POINT5DB,
LEVEL_MINUS_6DB,
LEVEL_MINUS_9DB
};
static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LEVEL_MINUS_6DB };
/**
* Table for center mix levels
* reference: Section 5.4.2.4 cmixlev
*/
static const uint8_t clevs[4] = { 2, 3, 4, 3 };
/**
* Table for surround mix levels
* reference: Section 5.4.2.5 surmixlev
*/
static const uint8_t slevs[4] = { 2, 4, 0, 4 };
/**
* Table for default stereo downmixing coefficients
* reference: Section 7.8.2 Downmixing Into Two Channels
*/
static const uint8_t ac3_default_coeffs[8][5][2] = {
{ { 1, 0 }, { 0, 1 }, },
{ { 2, 2 }, },
{ { 1, 0 }, { 0, 1 }, },
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, },
{ { 1, 0 }, { 0, 1 }, { 4, 4 }, },
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, },
{ { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
};
/* override ac3.h to include coupling channel */
#undef AC3_MAX_CHANNELS
@ -94,8 +125,6 @@ static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LE
typedef struct {
int acmod;
int cmixlev;
int surmixlev;
int dsurmod;
int blksw[AC3_MAX_CHANNELS];
@ -129,6 +158,7 @@ typedef struct {
int output_mode; ///< output channel configuration
int out_channels; ///< number of output channels
float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
float dynrng; //dynamic range gain
float dynrng2; //dynamic range gain for 1+1 mode
float cplco[AC3_MAX_CHANNELS][18]; //coupling coordinates
@ -286,6 +316,7 @@ static int ac3_parse_header(AC3DecodeContext *ctx)
{
AC3HeaderInfo hdr;
GetBitContext *gb = &ctx->gb;
float cmixlev, surmixlev;
int err, i;
err = ff_ac3_parse_header(gb->buffer, &hdr);
@ -295,8 +326,8 @@ static int ac3_parse_header(AC3DecodeContext *ctx)
/* get decoding parameters from header info */
ctx->bit_alloc_params.fscod = hdr.fscod;
ctx->acmod = hdr.acmod;
ctx->cmixlev = hdr.cmixlev;
ctx->surmixlev = hdr.surmixlev;
cmixlev = gain_levels[clevs[hdr.cmixlev]];
surmixlev = gain_levels[slevs[hdr.surmixlev]];
ctx->dsurmod = hdr.dsurmod;
ctx->lfeon = hdr.lfeon;
ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
@ -355,6 +386,24 @@ static int ac3_parse_header(AC3DecodeContext *ctx)
} while(i--);
}
/* set stereo downmixing coefficients
reference: Section 7.8.2 Downmixing Into Two Channels */
for(i=0; i<ctx->nfchans; i++) {
ctx->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[ctx->acmod][i][0]];
ctx->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[ctx->acmod][i][1]];
}
if(ctx->acmod > 1 && ctx->acmod & 1) {
ctx->downmix_coeffs[1][0] = ctx->downmix_coeffs[1][1] = cmixlev;
}
if(ctx->acmod == AC3_ACMOD_2F1R || ctx->acmod == AC3_ACMOD_3F1R) {
int nf = ctx->acmod - 2;
ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf][1] = surmixlev * LEVEL_MINUS_3DB;
}
if(ctx->acmod == AC3_ACMOD_2F2R || ctx->acmod == AC3_ACMOD_3F2R) {
int nf = ctx->acmod - 4;
ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf+1][1] = surmixlev;
}
return 0;
}
@ -662,12 +711,40 @@ static inline void do_imdct(AC3DecodeContext *ctx)
ctx->tmp_imdct);
}
ctx->dsp.vector_fmul_add_add(ctx->output[ch-1], ctx->tmp_output,
ctx->window, ctx->delay[ch-1], ctx->add_bias, 256, 1);
ctx->window, ctx->delay[ch-1], 0, 256, 1);
ctx->dsp.vector_fmul_reverse(ctx->delay[ch-1], ctx->tmp_output+256,
ctx->window, 256);
}
}
/**
* Downmixes the output to stereo.
*/
static void ac3_downmix(float samples[AC3_MAX_CHANNELS][256], int nfchans,
int output_mode, float coef[AC3_MAX_CHANNELS][2])
{
int i, j;
float v0, v1, s0, s1;
for(i=0; i<256; i++) {
v0 = v1 = s0 = s1 = 0.0f;
for(j=0; j<nfchans; j++) {
v0 += samples[j][i] * coef[j][0];
v1 += samples[j][i] * coef[j][1];
s0 += coef[j][0];
s1 += coef[j][1];
}
v0 /= s0;
v1 /= s1;
if(output_mode == AC3_ACMOD_MONO) {
samples[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
} else if(output_mode == AC3_ACMOD_STEREO) {
samples[0][i] = v0;
samples[1][i] = v1;
}
}
}
/* Parse the audio block from ac3 bitstream.
* This function extract the audio block from the ac3 bitstream
* and produces the output for the block. This function must
@ -945,8 +1022,18 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
do_imdct(ctx);
/* downmix output if needed */
if(ctx->nchans != ctx->out_channels && !((ctx->output_mode & AC3_OUTPUT_LFEON) &&
ctx->nfchans == ctx->out_channels)) {
ac3_downmix(ctx->output, ctx->nfchans, ctx->output_mode,
ctx->downmix_coeffs);
}
/* convert float to 16-bit integer */
for(ch=0; ch<ctx->out_channels; ch++) {
for(i=0; i<256; i++) {
ctx->output[ch][i] += ctx->add_bias;
}
ctx->dsp.float_to_int16(ctx->int_output[ch], ctx->output[ch], 256);
}
@ -981,14 +1068,24 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
avctx->bit_rate = ctx->bit_rate;
/* channel config */
ctx->out_channels = ctx->nchans;
if (avctx->channels == 0) {
avctx->channels = ctx->out_channels;
}
if(avctx->channels != ctx->out_channels) {
av_log(avctx, AV_LOG_ERROR, "Cannot mix AC3 to %d channels.\n",
avctx->channels);
} else if(ctx->out_channels < avctx->channels) {
av_log(avctx, AV_LOG_ERROR, "Cannot upmix AC3 from %d to %d channels.\n",
ctx->out_channels, avctx->channels);
return -1;
}
if(avctx->channels == 2) {
ctx->output_mode = AC3_ACMOD_STEREO;
} else if(avctx->channels == 1) {
ctx->output_mode = AC3_ACMOD_MONO;
} else if(avctx->channels != ctx->out_channels) {
av_log(avctx, AV_LOG_ERROR, "Cannot downmix AC3 from %d to %d channels.\n",
ctx->out_channels, avctx->channels);
return -1;
}
ctx->out_channels = avctx->channels;
//av_log(avctx, AV_LOG_INFO, "channels = %d \t bit rate = %d \t sampling rate = %d \n", avctx->channels, avctx->bit_rate * 1000, avctx->sample_rate);