Commit 24761399 authored by Justin Ruggles's avatar Justin Ruggles

move AC-3 header parsing to ac3.c

Originally committed as revision 8323 to svn://svn.ffmpeg.org/ffmpeg/trunk
parent c81ab015
......@@ -27,6 +27,7 @@
#include "avcodec.h"
#include "ac3.h"
#include "ac3tab.h"
#include "bitstream.h"
static inline int calc_lowcomp1(int a, int b0, int b1, int c)
{
......@@ -208,3 +209,53 @@ void ac3_common_init(void)
ff_ac3_frame_sizes[i][2] = ( 3*br );
}
}
int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
{
GetBitContext gbc;
memset(hdr, 0, sizeof(*hdr));
init_get_bits(&gbc, buf, 54);
hdr->sync_word = get_bits(&gbc, 16);
if(hdr->sync_word != 0x0B77)
return -1;
/* read ahead to bsid to make sure this is AC-3, not E-AC-3 */
hdr->bsid = show_bits_long(&gbc, 29) & 0x1F;
if(hdr->bsid > 10)
return -2;
hdr->crc1 = get_bits(&gbc, 16);
hdr->fscod = get_bits(&gbc, 2);
if(hdr->fscod == 3)
return -3;
hdr->frmsizecod = get_bits(&gbc, 6);
if(hdr->frmsizecod > 37)
return -4;
skip_bits(&gbc, 5); // skip bsid, already got it
hdr->bsmod = get_bits(&gbc, 3);
hdr->acmod = get_bits(&gbc, 3);
if((hdr->acmod & 1) && hdr->acmod != 1) {
hdr->cmixlev = get_bits(&gbc, 2);
}
if(hdr->acmod & 4) {
hdr->surmixlev = get_bits(&gbc, 2);
}
if(hdr->acmod == 2) {
hdr->dsurmod = get_bits(&gbc, 2);
}
hdr->lfeon = get_bits1(&gbc);
hdr->halfratecod = FFMAX(hdr->bsid, 8) - 8;
hdr->sample_rate = ff_ac3_freqs[hdr->fscod] >> hdr->halfratecod;
hdr->bit_rate = (ff_ac3_bitratetab[hdr->frmsizecod>>1] * 1000) >> hdr->halfratecod;
hdr->channels = ff_ac3_channels[hdr->acmod] + hdr->lfeon;
hdr->frame_size = ff_ac3_frame_sizes[hdr->frmsizecod][hdr->fscod] * 2;
return 0;
}
......@@ -45,6 +45,50 @@ typedef struct AC3BitAllocParameters {
int cplfleak, cplsleak;
} AC3BitAllocParameters;
/**
* @struct AC3HeaderInfo
* Coded AC-3 header values up to the lfeon element, plus derived values.
*/
typedef struct {
/** @defgroup coded Coded elements
* @{
*/
uint16_t sync_word;
uint16_t crc1;
uint8_t fscod;
uint8_t frmsizecod;
uint8_t bsid;
uint8_t bsmod;
uint8_t acmod;
uint8_t cmixlev;
uint8_t surmixlev;
uint8_t dsurmod;
uint8_t lfeon;
/** @} */
/** @defgroup derived Derived values
* @{
*/
uint8_t halfratecod;
uint16_t sample_rate;
uint32_t bit_rate;
uint8_t channels;
uint16_t frame_size;
/** @} */
} AC3HeaderInfo;
/**
* Parses AC-3 frame header.
* Parses the header up to the lfeon element, which is the first 52 or 54 bits
* depending on the audio coding mode.
* @param buf[in] Array containing the first 7 bytes of the frame.
* @param hdr[out] Pointer to struct where header info is written.
* @return Returns 0 on success, -1 if there is a sync word mismatch,
* -2 if the bsid (version) element is invalid, -3 if the fscod (sample rate)
* element is invalid, or -4 if the frmsizecod (bit rate) element is invalid.
*/
int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr);
extern uint16_t ff_ac3_frame_sizes[38][3];
extern const uint8_t ff_ac3_channels[8];
extern const uint16_t ff_ac3_freqs[3];
......
......@@ -604,43 +604,26 @@ static const int aac_channels[8] = {
static int ac3_sync(const uint8_t *buf, int *channels, int *sample_rate,
int *bit_rate, int *samples)
{
unsigned int fscod, frmsizecod, acmod, bsid, lfeon, halfratecod;
int err;
unsigned int fscod, acmod, bsid, lfeon;
unsigned int strmtyp, substreamid, frmsiz, fscod2, numblkscod;
GetBitContext bits;
AC3HeaderInfo hdr;
init_get_bits(&bits, buf, AC3_HEADER_SIZE * 8);
err = ff_ac3_parse_header(buf, &hdr);
if(get_bits(&bits, 16) != 0x0b77)
if(err < 0 && err != -2)
return 0;
bsid = show_bits_long(&bits, 29) & 0x1f;
bsid = hdr.bsid;
if(bsid <= 10) { /* Normal AC-3 */
skip_bits(&bits, 16); /* crc */
fscod = get_bits(&bits, 2);
frmsizecod = get_bits(&bits, 6);
if(fscod == 3 && frmsizecod > 37)
return 0;
skip_bits(&bits, 5); /* bsid */
skip_bits(&bits, 3); /* bsmod */
acmod = get_bits(&bits, 3);
if(acmod & 1 && acmod != 1)
skip_bits(&bits, 2); /* cmixlev */
if(acmod & 4)
skip_bits(&bits, 2); /* surmixlev */
if(acmod & 2)
skip_bits(&bits, 2); /* dsurmod */
lfeon = get_bits1(&bits);
halfratecod = FFMAX(bsid, 8) - 8;
*sample_rate = ff_ac3_freqs[fscod] >> halfratecod;
*bit_rate = (ff_ac3_bitratetab[frmsizecod] * 1000) >> halfratecod;
*channels = ff_ac3_channels[acmod] + lfeon;
*samples = 6 * 256;
return ff_ac3_frame_sizes[frmsizecod][fscod] * 2;
*sample_rate = hdr.sample_rate;
*bit_rate = hdr.bit_rate;
*channels = hdr.channels;
*samples = AC3_FRAME_SIZE;
return hdr.frame_size;
} else if (bsid > 10 && bsid <= 16) { /* Enhanced AC-3 */
init_get_bits(&bits, &buf[2], (AC3_HEADER_SIZE-2) * 8);
strmtyp = get_bits(&bits, 2);
substreamid = get_bits(&bits, 3);
......
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