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| author | Justin Ruggles <justin.ruggles@gmail.com> | 2007-12-28 06:13:55 +0000 |
|---|---|---|
| committer | Justin Ruggles <justin.ruggles@gmail.com> | 2007-12-28 06:13:55 +0000 |
| commit | 02c164c1482e16715716b2615964481877412e4b (patch) | |
| tree | 0ce15124dfd2f81e15ea04b4648ec917eae13cbc /libavcodec/ac3enc.c | |
| parent | 08ac1e783e5160257fe58aec5b0ca611ab8c7498 (diff) | |
use cutoff frequency to adjust bandwidth in ac3 encoder
Originally committed as revision 11338 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/ac3enc.c')
| -rw-r--r-- | libavcodec/ac3enc.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c index e84b220dc8..4ed58e7e84 100644 --- a/libavcodec/ac3enc.c +++ b/libavcodec/ac3enc.c @@ -632,6 +632,7 @@ static int AC3_encode_init(AVCodecContext *avctx) AC3EncodeContext *s = avctx->priv_data; int i, j, ch; float alpha; + int bw_code; static const uint8_t channel_mode_defs[6] = { 0x01, /* C */ 0x02, /* L R */ @@ -683,12 +684,21 @@ static int AC3_encode_init(AVCodecContext *avctx) s->frame_size = s->frame_size_min; /* bit allocation init */ - for(ch=0;ch<s->nb_channels;ch++) { - /* bandwidth for each channel */ + if(avctx->cutoff) { + /* calculate bandwidth based on user-specified cutoff frequency */ + int cutoff = av_clip(avctx->cutoff, 1, s->sample_rate >> 1); + int fbw_coeffs = cutoff * 512 / s->sample_rate; + 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 anoying high freq artefacts */ - s->chbwcod[ch] = 50; /* sample bandwidth as mpeg audio layer 2 table 0 */ - s->nb_coefs[ch] = ((s->chbwcod[ch] + 12) * 3) + 37; + bw_code = 50; + } + for(ch=0;ch<s->nb_channels;ch++) { + /* bandwidth for each channel */ + s->chbwcod[ch] = bw_code; + s->nb_coefs[ch] = bw_code * 3 + 73; } if (s->lfe) { s->nb_coefs[s->lfe_channel] = 7; /* fixed */ |