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ffmpeg.wasm-core
Commit 9fc1ab72 authored by Justin Ruggles's avatar Justin Ruggles
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Use shared AC-3 header parsing. Move some initializations to block parsing function. 

Originally committed as revision 9773 to svn://svn.ffmpeg.org/ffmpeg/trunk
parent 9ef60390
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Showing with 62 additions and 90 deletions
libavcodec/ac3dec.c
View file @ 9fc1ab72
......@@ -33,8 +33,7 @@
#include <string.h>
#include "avcodec.h"
#include "ac3.h"
#include "ac3tab.h"
#include "ac3_parser.h"
#include "bitstream.h"
#include "dsputil.h"
#include "random.h"
......@@ -89,9 +88,6 @@ static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LE
#define AC3_OUTPUT_LFEON 0x10
typedef struct {
uint16_t crc1;
uint8_t fscod;
uint8_t acmod;
uint8_t cmixlev;
uint8_t surmixlev;
......@@ -141,7 +137,8 @@ typedef struct {
int bit_rate;
int frame_size;
int nfchans; //number of channels
int nchans; //number of total channels
int nfchans; //number of full-bandwidth channels
int lfeon; //lfe channel in use
float dynrng; //dynamic range gain
......@@ -320,87 +317,54 @@ static int ac3_decode_init(AVCodecContext *avctx)
}
/*********** END INIT FUNCTIONS ***********/
/* Parse the 'sync_info' from the ac3 bitstream.
* This function extracts the sync_info from ac3 bitstream.
/**
* Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
* GetBitContext within AC3DecodeContext must point to
* start of the synchronized ac3 bitstream.
*
* @param ctx AC3DecodeContext
* @return Returns framesize, returns 0 if fscod, frmsizecod or bsid is not valid
*/
static int ac3_parse_sync_info(AC3DecodeContext *ctx)
static int ac3_parse_header(AC3DecodeContext *ctx)
{
AC3HeaderInfo hdr;
GetBitContext *gb = &ctx->gb;
int frmsizecod, bsid;
int err, i;
err = ff_ac3_parse_header(gb->buffer, &hdr);
if(err)
return err;
/* 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;
ctx->dsurmod = hdr.dsurmod;
ctx->lfeon = hdr.lfeon;
ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
ctx->sampling_rate = hdr.sample_rate;
ctx->bit_rate = hdr.bit_rate;
ctx->nchans = hdr.channels;
ctx->nfchans = ctx->nchans - ctx->lfeon;
ctx->frame_size = hdr.frame_size;
ctx->blkoutput = nfchans_tbl[ctx->acmod];
if(ctx->lfeon)
ctx->blkoutput |= AC3_OUTPUT_LFEON;
/* skip over portion of header which has already been read */
skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
ctx->crc1 = get_bits(gb, 16);
ctx->fscod = get_bits(gb, 2);
if (ctx->fscod == 0x03)
return 0;
frmsizecod = get_bits(gb, 6);
if (frmsizecod >= 38)
return 0;
ctx->sampling_rate = ff_ac3_freqs[ctx->fscod];
ctx->bit_rate = ff_ac3_bitratetab[frmsizecod >> 1];
/* we include it here in order to determine validity of ac3 frame */
bsid = get_bits(gb, 5);
if (bsid > 0x08)
return 0;
skip_bits(gb, 3); //skip the bsmod, bsi->bsmod = get_bits(gb, 3);
switch (ctx->fscod) {
case 0x00:
ctx->frame_size = 4 * ctx->bit_rate;
return ctx->frame_size;
case 0x01:
ctx->frame_size = 2 * (320 * ctx->bit_rate / 147 + (frmsizecod & 1));
return ctx->frame_size;
case 0x02:
ctx->frame_size = 6 * ctx->bit_rate;
return ctx->frame_size;
}
/* never reached */
return 0;
}
/* Parse bsi from ac3 bitstream.
* This function extracts the bitstream information (bsi) from ac3 bitstream.
*
* @param ctx AC3DecodeContext after processed by ac3_parse_sync_info
*/
static void ac3_parse_bsi(AC3DecodeContext *ctx)
{
GetBitContext *gb = &ctx->gb;
int i;
ctx->cmixlev = 0;
ctx->surmixlev = 0;
ctx->dsurmod = 0;
ctx->nfchans = 0;
ctx->cpldeltbae = DBA_NONE;
ctx->cpldeltnseg = 0;
for (i = 0; i < 5; i++) {
ctx->deltbae[i] = DBA_NONE;
ctx->deltnseg[i] = 0;
skip_bits(gb, 16); // skip crc1
skip_bits(gb, 8); // skip fscod and frmsizecod
skip_bits(gb, 11); // skip bsid, bsmod, and acmod
if(ctx->acmod == AC3_ACMOD_STEREO) {
skip_bits(gb, 2); // skip dsurmod
} else {
if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
skip_bits(gb, 2); // skip cmixlev
if(ctx->acmod & 4)
skip_bits(gb, 2); // skip surmixlev
}
ctx->dynrng = 1.0;
ctx->dynrng2 = 1.0;
ctx->acmod = get_bits(gb, 3);
ctx->nfchans = nfchans_tbl[ctx->acmod];
if (ctx->acmod & 0x01 && ctx->acmod != 0x01)
ctx->cmixlev = get_bits(gb, 2);
if (ctx->acmod & 0x04)
ctx->surmixlev = get_bits(gb, 2);
if (ctx->acmod == 0x02)
ctx->dsurmod = get_bits(gb, 2);
ctx->lfeon = get_bits1(gb);
skip_bits1(gb); // skip lfeon
/* read the rest of the bsi. read twice for dual mono mode. */
i = !(ctx->acmod);
do {
skip_bits(gb, 5); //skip dialog normalization
......@@ -414,6 +378,7 @@ static void ac3_parse_bsi(AC3DecodeContext *ctx)
skip_bits(gb, 2); //skip copyright bit and original bitstream bit
/* FIXME: read & use the xbsi1 downmix levels */
if (get_bits1(gb))
skip_bits(gb, 14); //skip timecode1
if (get_bits1(gb))
......@@ -425,6 +390,8 @@ static void ac3_parse_bsi(AC3DecodeContext *ctx)
skip_bits(gb, 8);
} while(i--);
}
return 0;
}
/**
......@@ -1339,7 +1306,7 @@ static inline void do_imdct(AC3DecodeContext *ctx)
* and produces the output for the block. This function must
* be called for each of the six audio block in the ac3 bitstream.
*/
static int ac3_parse_audio_block(AC3DecodeContext * ctx)
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
{
int nfchans = ctx->nfchans;
int acmod = ctx->acmod;
......@@ -1361,11 +1328,17 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
if (get_bits1(gb)) { /* dynamic range */
dynrng = get_sbits(gb, 8);
ctx->dynrng = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
} else if(blk == 0) {
ctx->dynrng = 1.0;
}
if (acmod == 0x00 && get_bits1(gb)) { /* dynamic range 1+1 mode */
if(acmod == AC3_ACMOD_DUALMONO) { /* dynamic range 1+1 mode */
if(get_bits1(gb)) {
dynrng = get_sbits(gb, 8);
ctx->dynrng2 = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
} else if(blk == 0) {
ctx->dynrng2 = 1.0;
}
}
get_downmix_coeffs(ctx);
......@@ -1559,12 +1532,16 @@ static int ac3_parse_audio_block(AC3DecodeContext * ctx)
ctx->deltba[i][seg] = get_bits(gb, 3);
}
}
} else if(blk == 0) {
if(ctx->cplinu)
ctx->cpldeltbae = DBA_NONE;
for(i=0; i<nfchans; i++) {
ctx->deltbae[i] = DBA_NONE;
}
}
if (bit_alloc_flags) {
/* set bit allocation parameters */
ctx->bit_alloc_params.fscod = ctx->fscod;
ctx->bit_alloc_params.halfratecod = 0;
ctx->bit_alloc_params.sdecay = ff_sdecaytab[ctx->sdcycod];
ctx->bit_alloc_params.fdecay = ff_fdecaytab[ctx->fdcycod];
ctx->bit_alloc_params.sgain = ff_sgaintab[ctx->sgaincod];
......@@ -1638,17 +1615,12 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
init_get_bits(&ctx->gb, buf, buf_size * 8);
//Parse the syncinfo.
//If 'fscod' or 'bsid' is not valid the decoder shall mute as per the standard.
if (!ac3_parse_sync_info(ctx)) {
if (ac3_parse_header(ctx)) {
av_log(avctx, AV_LOG_ERROR, "\n");
*data_size = 0;
return buf_size;
}
//Parse the BSI.
//If 'bsid' is not valid decoder shall not decode the audio as per the standard.
ac3_parse_bsi(ctx);
avctx->sample_rate = ctx->sampling_rate;
avctx->bit_rate = ctx->bit_rate;
......@@ -1679,7 +1651,7 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
//Parse the Audio Blocks.
for (i = 0; i < NB_BLOCKS; i++) {
if (ac3_parse_audio_block(ctx)) {
if (ac3_parse_audio_block(ctx, i)) {
av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
*data_size = 0;
return ctx->frame_size;
......
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