Commit e05a3ac7 authored by Justin Ruggles's avatar Justin Ruggles
Browse files

ac3enc: select bandwidth based on bit rate, sample rate, and number of

full-bandwidth channels.

This reduces high-frequency artifacts and improves the quality of the lower
frequency audio at low bit rates.
parent e3c007bb
......@@ -329,6 +329,36 @@ static const int64_t ac3_channel_layouts[] = {
};
/**
* LUT to select the bandwidth code based on the bit rate, sample rate, and
* number of full-bandwidth channels.
* bandwidth_tab[fbw_channels-1][sample rate code][bit rate code]
*/
static const uint8_t ac3_bandwidth_tab[5][3][19] = {
// 32 40 48 56 64 80 96 112 128 160 192 224 256 320 384 448 512 576 640
{ { 0, 0, 0, 12, 16, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 16, 20, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 32, 40, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 20, 24, 32, 48, 48, 48, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 4, 24, 28, 36, 56, 56, 56, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 20, 44, 52, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 24, 32, 40, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 4, 20, 28, 36, 44, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 20, 40, 48, 60, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 24, 32, 48, 48, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 28, 36, 56, 56, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 32, 48, 60, 60, 60, 60, 60, 60, 60 } },
{ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 20, 32, 40, 48, 48, 48, 48 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 24, 36, 44, 56, 56, 56, 56 },
{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 28, 44, 60, 60, 60, 60, 60, 60 } }
};
/**
* Adjust the frame size to make the average bit rate match the target bit rate.
* This is only needed for 11025, 22050, and 44100 sample rates.
......@@ -2095,9 +2125,7 @@ static av_cold void set_bandwidth(AC3EncodeContext *s)
bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
} else {
/* use default bandwidth setting */
/* XXX: should compute the bandwidth according to the frame
size, so that we avoid annoying high frequency artifacts */
bw_code = 50;
bw_code = ac3_bandwidth_tab[s->fbw_channels-1][s->bit_alloc.sr_code][s->frame_size_code/2];
}
/* set number of coefficients for each channel */
......
408f47ee5a60866fc751f7bc2314cbd6 *./tests/data/acodec/ac3.rm
5ddb6d25dd117db29627f9d286153a7a *./tests/data/acodec/ac3.rm
98751 ./tests/data/acodec/ac3.rm
da74fe749c2eb21bbead7de81d2f3078 *./tests/data/lavf/lavf.rm
a1c71456f21d5459d2824d75bbdcc80c *./tests/data/lavf/lavf.rm
346706 ./tests/data/lavf/lavf.rm
......@@ -5,7 +5,8 @@ ret:-1 st:-1 flags:1 ts: 1.894167
ret:-1 st: 0 flags:0 ts: 0.788000
ret: 0 st: 0 flags:1 ts:-0.317000
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 271 size: 556
ret:-1 st:-1 flags:0 ts: 2.576668
ret: 0 st:-1 flags:0 ts: 2.576668
ret: 0 st: 0 flags:1 dts: 2.577000 pts: 2.577000 pos: 42397 size: 558
ret:-1 st:-1 flags:1 ts: 1.470835
ret:-1 st: 0 flags:0 ts: 0.365000
ret: 0 st: 0 flags:1 ts:-0.741000
......@@ -19,7 +20,8 @@ ret:-1 st:-1 flags:0 ts: 1.730004
ret:-1 st:-1 flags:1 ts: 0.624171
ret: 0 st: 0 flags:0 ts:-0.482000
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 271 size: 556
ret:-1 st: 0 flags:1 ts: 2.413000
ret: 0 st: 0 flags:1 ts: 2.413000
ret: 0 st: 0 flags:1 dts: 2.368000 pts: 2.368000 pos: 38981 size: 558
ret:-1 st:-1 flags:0 ts: 1.306672
ret:-1 st:-1 flags:1 ts: 0.200839
ret: 0 st: 0 flags:0 ts:-0.905000
......@@ -28,7 +30,8 @@ ret:-1 st: 0 flags:1 ts: 1.989000
ret:-1 st:-1 flags:0 ts: 0.883340
ret: 0 st:-1 flags:1 ts:-0.222493
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 271 size: 556
ret:-1 st: 0 flags:0 ts: 2.672000
ret: 0 st: 0 flags:0 ts: 2.672000
ret: 0 st: 0 flags:1 dts: 2.821000 pts: 2.821000 pos: 46383 size: 556
ret:-1 st: 0 flags:1 ts: 1.566000
ret:-1 st:-1 flags:0 ts: 0.460008
ret: 0 st:-1 flags:1 ts:-0.645825
......
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