[Ffmpeg-cvslog] r8323 - in trunk/libavcodec: ac3.c ac3.h parser.c
jbr
subversion
Sun Mar 11 17:44:15 CET 2007
Author: jbr
Date: Sun Mar 11 17:44:14 2007
New Revision: 8323
Modified:
trunk/libavcodec/ac3.c
trunk/libavcodec/ac3.h
trunk/libavcodec/parser.c
Log:
move AC-3 header parsing to ac3.c
Modified: trunk/libavcodec/ac3.c
==============================================================================
--- trunk/libavcodec/ac3.c (original)
+++ trunk/libavcodec/ac3.c Sun Mar 11 17:44:14 2007
@@ -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;
+}
Modified: trunk/libavcodec/ac3.h
==============================================================================
--- trunk/libavcodec/ac3.h (original)
+++ trunk/libavcodec/ac3.h Sun Mar 11 17:44:14 2007
@@ -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];
Modified: trunk/libavcodec/parser.c
==============================================================================
--- trunk/libavcodec/parser.c (original)
+++ trunk/libavcodec/parser.c Sun Mar 11 17:44:14 2007
@@ -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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