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ac3dec: Move center&surround mix level tables to parser.

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That way all mix levels as exported by the parser
will have the same meaning.

Previously the 3bit center mix level for eac3 was
used to index in a 4 entry table leading to out of array reads.
this change removes the table and offsets the ac3 variable by 4
so it matches the meanings for eac3 except the reserved case.
The reserved case is then explicitly handled.

Idea-by: Justin Ruggles <justin.ruggles@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2012-01-19 00:06:03 +01:00
parent 9ec39937f9
commit 99a42f3fa9
2 changed files with 20 additions and 20 deletions
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20
libavcodec/ac3_parser.c
View File

@ -34,6 +34,18 @@ static const uint8_t eac3_blocks[4] = {
1, 2, 3, 6
};
/**
* Table for center mix levels
* reference: Section 5.4.2.4 cmixlev
*/
static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
/**
* Table for surround mix levels
* reference: Section 5.4.2.5 surmixlev
*/
static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
{
@ -53,8 +65,8 @@ int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
hdr->num_blocks = 6;
/* set default mix levels */
hdr->center_mix_level = 1; // -4.5dB
hdr->surround_mix_level = 1; // -6.0dB
hdr->center_mix_level = 5; // -4.5dB
hdr->surround_mix_level = 6; // -6.0dB
if(hdr->bitstream_id <= 10) {
/* Normal AC-3 */
@ -76,9 +88,9 @@ int avpriv_ac3_parse_header(GetBitContext *gbc, AC3HeaderInfo *hdr)
skip_bits(gbc, 2); // skip dsurmod
} else {
if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO)
hdr->center_mix_level = get_bits(gbc, 2);
hdr-> center_mix_level = center_levels[get_bits(gbc, 2)];
if(hdr->channel_mode & 4)
hdr->surround_mix_level = get_bits(gbc, 2);
hdr->surround_mix_level = surround_levels[get_bits(gbc, 2)];
}
hdr->lfe_on = get_bits1(gbc);

20
libavcodec/ac3dec.c
View File

@ -76,18 +76,6 @@ static const float gain_levels[9] = {
LEVEL_MINUS_9DB
};
/**
* Table for center mix levels
* reference: Section 5.4.2.4 cmixlev
*/
static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
/**
* Table for surround mix levels
* reference: Section 5.4.2.5 surmixlev
*/
static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
/**
* Table for default stereo downmixing coefficients
* reference: Section 7.8.2 Downmixing Into Two Channels
@ -320,8 +308,8 @@ static int parse_frame_header(AC3DecodeContext *s)
static void set_downmix_coeffs(AC3DecodeContext *s)
{
int i;
float cmix = gain_levels[center_levels[s->center_mix_level]];
float smix = gain_levels[surround_levels[s->surround_mix_level]];
float cmix = gain_levels[s-> center_mix_level];
float smix = gain_levels[s->surround_mix_level];
float norm0, norm1;
for (i = 0; i < s->fbw_channels; i++) {
@ -1400,8 +1388,8 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data,
avctx->channels = s->out_channels;
avctx->channel_layout = s->channel_layout;
s->loro_center_mix_level = gain_levels[ center_levels[s-> center_mix_level]];
s->loro_surround_mix_level = gain_levels[surround_levels[s->surround_mix_level]];
s->loro_center_mix_level = gain_levels[s-> center_mix_level];
s->loro_surround_mix_level = gain_levels[s->surround_mix_level];
s->ltrt_center_mix_level = LEVEL_MINUS_3DB;
s->ltrt_surround_mix_level = LEVEL_MINUS_3DB;
/* set downmixing coefficients if needed */