1, 2, 3, 6
};
+/**
+ * Table for center mix levels
+ * reference: Section 5.4.2.4 cmixlev
+ */
+static const uint8_t center_levels[4] = { 2, 3, 4, 3 };
+
+/**
+ * Table for surround mix levels
+ * reference: Section 5.4.2.5 surmixlev
+ */
+static const uint8_t surround_levels[4] = { 2, 4, 0, 4 };
-int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
+
+int ff_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
{
- GetBitContext gbc;
int frame_size_code;
int num_blocks;
memset(hdr, 0, sizeof(*hdr));
- init_get_bits(&gbc, buf, 54);
-
- hdr->sync_word = get_bits(&gbc, 16);
+ hdr->sync_word = get_bits(gbc, 16);
if(hdr->sync_word != 0x0B77)
return AC3_PARSE_ERROR_SYNC;
/* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
- hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
+ hdr->bitstream_id = show_bits_long(gbc, 29) & 0x1F;
if(hdr->bitstream_id > 16)
return AC3_PARSE_ERROR_BSID;
if(hdr->bitstream_id <= 10) {
/* Normal AC-3 */
- hdr->crc1 = get_bits(&gbc, 16);
- hdr->sr_code = get_bits(&gbc, 2);
+ hdr->crc1 = get_bits(gbc, 16);
+ hdr->sr_code = get_bits(gbc, 2);
if(hdr->sr_code == 3)
return AC3_PARSE_ERROR_SAMPLE_RATE;
- frame_size_code = get_bits(&gbc, 6);
+ frame_size_code = get_bits(gbc, 6);
if(frame_size_code > 37)
return AC3_PARSE_ERROR_FRAME_SIZE;
- skip_bits(&gbc, 5); // skip bsid, already got it
+ skip_bits(gbc, 5); // skip bsid, already got it
+
+ skip_bits(gbc, 3); // skip bitstream mode
+ hdr->channel_mode = get_bits(gbc, 3);
+
+ /* set default mix levels */
+ hdr->center_mix_level = 3; // -4.5dB
+ hdr->surround_mix_level = 4; // -6.0dB
- skip_bits(&gbc, 3); // skip bitstream mode
- hdr->channel_mode = get_bits(&gbc, 3);
- if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) {
- skip_bits(&gbc, 2); // skip center mix level
- }
- if(hdr->channel_mode & 4) {
- skip_bits(&gbc, 2); // skip surround mix level
- }
if(hdr->channel_mode == AC3_CHMODE_STEREO) {
- skip_bits(&gbc, 2); // skip dolby surround mode
+ skip_bits(gbc, 2); // skip dsurmod
+ } else {
+ if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
+ hdr->center_mix_level = center_levels[get_bits(gbc, 2)];
+ if(hdr->channel_mode & 4)
+ hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
}
- hdr->lfe_on = get_bits1(&gbc);
+ hdr->lfe_on = get_bits1(gbc);
hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
} else {
/* Enhanced AC-3 */
hdr->crc1 = 0;
- hdr->frame_type = get_bits(&gbc, 2);
+ hdr->frame_type = get_bits(gbc, 2);
if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
return AC3_PARSE_ERROR_FRAME_TYPE;
- skip_bits(&gbc, 3); // skip substream id
+ skip_bits(gbc, 3); // skip substream id
- hdr->frame_size = (get_bits(&gbc, 11) + 1) << 1;
+ hdr->frame_size = (get_bits(gbc, 11) + 1) << 1;
if(hdr->frame_size < AC3_HEADER_SIZE)
return AC3_PARSE_ERROR_FRAME_SIZE;
- hdr->sr_code = get_bits(&gbc, 2);
+ hdr->sr_code = get_bits(gbc, 2);
if (hdr->sr_code == 3) {
- int sr_code2 = get_bits(&gbc, 2);
+ int sr_code2 = get_bits(gbc, 2);
if(sr_code2 == 3)
return AC3_PARSE_ERROR_SAMPLE_RATE;
hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
hdr->sr_shift = 1;
num_blocks = 6;
} else {
- num_blocks = eac3_blocks[get_bits(&gbc, 2)];
+ num_blocks = eac3_blocks[get_bits(gbc, 2)];
hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
hdr->sr_shift = 0;
}
- hdr->channel_mode = get_bits(&gbc, 3);
- hdr->lfe_on = get_bits1(&gbc);
+ hdr->channel_mode = get_bits(gbc, 3);
+ hdr->lfe_on = get_bits1(gbc);
hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
(num_blocks * 256.0));
int err;
uint64_t tmp = be2me_64(state);
AC3HeaderInfo hdr;
+ GetBitContext gbc;
- err = ff_ac3_parse_header(((uint8_t *)&tmp)+8-AC3_HEADER_SIZE, &hdr);
+ init_get_bits(&gbc, ((uint8_t *)&tmp)+8-AC3_HEADER_SIZE, 54);
+ err = ff_ac3_parse_header(&gbc, &hdr);
if(err < 0)
return 0;
};
/**
- * Table for center mix levels
- * reference: Section 5.4.2.4 cmixlev
- */
-static const uint8_t center_levels[4] = { 2, 3, 4, 3 };
-
-/**
- * Table for surround mix levels
- * reference: Section 5.4.2.5 surmixlev
- */
-static const uint8_t surround_levels[4] = { 2, 4, 0, 4 };
-
-/**
* Table for default stereo downmixing coefficients
* reference: Section 7.8.2 Downmixing Into Two Channels
*/
GetBitContext *gbc = &s->gbc;
int err, i;
- err = ff_ac3_parse_header(gbc->buffer, &hdr);
+ err = ff_ac3_parse_header(gbc, &hdr);
if(err)
return err;
s->fbw_channels = s->channels - s->lfe_on;
s->lfe_ch = s->fbw_channels + 1;
s->frame_size = hdr.frame_size;
+ s->center_mix_level = hdr.center_mix_level;
+ s->surround_mix_level = hdr.surround_mix_level;
/* set default output to all source channels */
s->out_channels = s->channels;
if(s->lfe_on)
s->output_mode |= AC3_OUTPUT_LFEON;
- /* set default mix levels */
- s->center_mix_level = 3; // -4.5dB
- s->surround_mix_level = 4; // -6.0dB
-
- /* skip over portion of header which has already been read */
- skip_bits(gbc, 16); // skip the sync_word
- skip_bits(gbc, 16); // skip crc1
- skip_bits(gbc, 8); // skip fscod and frmsizecod
- skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
- if(s->channel_mode == AC3_CHMODE_STEREO) {
- skip_bits(gbc, 2); // skip dsurmod
- } else {
- if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
- s->center_mix_level = center_levels[get_bits(gbc, 2)];
- if(s->channel_mode & 4)
- s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
- }
- skip_bits1(gbc); // skip lfeon
-
/* read the rest of the bsi. read twice for dual mono mode. */
i = !(s->channel_mode);
do {