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author | Ian Braithwaite <ian@braithwaite.dk> | 2007-03-13 19:44:02 +0000 |
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committer | Benjamin Larsson <banan@ludd.ltu.se> | 2007-03-13 19:44:02 +0000 |
commit | 85e7386ae0d33ede4c575d4df4c1faae6c906338 (patch) | |
tree | eaf1e54e2143c041514129c7a4cfa275c74ba92e /libavcodec/cook.c | |
parent | e057461daca4ea83418fd359e9173a997270a00b (diff) | |
download | ffmpeg-streaming-85e7386ae0d33ede4c575d4df4c1faae6c906338.zip ffmpeg-streaming-85e7386ae0d33ede4c575d4df4c1faae6c906338.tar.gz |
Combine the window and overlap loops,
and get rid of the data swapping.
Patch by Ian Braithwaite <dk dot braithwaite at ian>
Originally committed as revision 8387 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/cook.c')
-rw-r--r-- | libavcodec/cook.c | 69 |
1 files changed, 28 insertions, 41 deletions
diff --git a/libavcodec/cook.c b/libavcodec/cook.c index 0a21945..eb8e5ed 100644 --- a/libavcodec/cook.c +++ b/libavcodec/cook.c @@ -685,33 +685,6 @@ static void mono_decode(COOKContext *q, float* mlt_buffer) { /** - * The modulated lapped transform, this takes transform coefficients - * and transforms them into timedomain samples. This is done through - * an FFT-based algorithm with pre- and postrotation steps. - * A window and reorder step is also included. - * - * @param q pointer to the COOKContext - * @param inbuffer pointer to the mltcoefficients - * @param outbuffer pointer to the timedomain buffer - * @param mlt_tmp pointer to temporary storage space - */ - -static void cook_imlt(COOKContext *q, float* inbuffer, float* outbuffer) -{ - int i; - - q->mdct_ctx.fft.imdct_calc(&q->mdct_ctx, outbuffer, inbuffer, q->mdct_tmp); - - for(i = 0; i < q->samples_per_channel; i++){ - float tmp = outbuffer[i]; - - outbuffer[i] = q->mlt_window[i] * outbuffer[q->samples_per_channel + i]; - outbuffer[q->samples_per_channel + i] = q->mlt_window[q->samples_per_channel - 1 - i] * -tmp; - } -} - - -/** * the actual requantization of the timedomain samples * * @param q pointer to the COOKContext @@ -743,36 +716,50 @@ static void interpolate(COOKContext *q, float* buffer, /** - * mlt overlapping and buffer management + * The modulated lapped transform, this takes transform coefficients + * and transforms them into timedomain samples. + * Apply transform window, overlap buffers, apply gain profile + * and buffer management. * * @param q pointer to the COOKContext + * @param inbuffer pointer to the mltcoefficients * @param gains_ptr current and previous gains * @param previous_buffer pointer to the previous buffer to be used for overlapping */ -static void gain_compensate(COOKContext *q, cook_gains *gains_ptr, - float* previous_buffer) +static void imlt_gain(COOKContext *q, float *inbuffer, + cook_gains *gains_ptr, float* previous_buffer) { const float fc = q->pow2tab[gains_ptr->previous[0] + 63]; - float *buffer = q->mono_mdct_output; + float *buffer0 = q->mono_mdct_output; + float *buffer1 = q->mono_mdct_output + q->samples_per_channel; int i; - /* Overlap with the previous block. */ - for(i=0 ; i<q->samples_per_channel ; i++) { - buffer[i] *= fc; - buffer[i] += previous_buffer[i]; + /* Inverse modified discrete cosine transform */ + q->mdct_ctx.fft.imdct_calc(&q->mdct_ctx, q->mono_mdct_output, + inbuffer, q->mdct_tmp); + + /* The weird thing here, is that the two halves of the time domain + * buffer are swapped. Also, the newest data, that we save away for + * next frame, has the wrong sign. Hence the subtraction below. + * Almost sounds like a complex conjugate/reverse data/FFT effect. + */ + + /* Apply window and overlap */ + for(i = 0; i < q->samples_per_channel; i++){ + buffer1[i] = buffer1[i] * fc * q->mlt_window[i] - + previous_buffer[i] * q->mlt_window[q->samples_per_channel - 1 - i]; } /* Apply gain profile */ for (i = 0; i < 8; i++) { if (gains_ptr->now[i] || gains_ptr->now[i + 1]) - interpolate(q, &buffer[q->gain_size_factor * i], + interpolate(q, &buffer1[q->gain_size_factor * i], gains_ptr->now[i], gains_ptr->now[i + 1]); } /* Save away the current to be previous block. */ - memcpy(previous_buffer, buffer+q->samples_per_channel, - sizeof(float)*q->samples_per_channel); + memcpy(previous_buffer, buffer0, sizeof(float)*q->samples_per_channel); } @@ -902,16 +889,16 @@ mlt_compensate_output(COOKContext *q, float *decode_buffer, cook_gains *gains, float *previous_buffer, int16_t *out, int chan) { + float *output = q->mono_mdct_output + q->samples_per_channel; int j; - cook_imlt(q, decode_buffer, q->mono_mdct_output); - gain_compensate(q, gains, previous_buffer); + imlt_gain(q, decode_buffer, gains, previous_buffer); /* Clip and convert floats to 16 bits. */ for (j = 0; j < q->samples_per_channel; j++) { out[chan + q->nb_channels * j] = - av_clip(lrintf(q->mono_mdct_output[j]), -32768, 32767); + av_clip(lrintf(output[j]), -32768, 32767); } } |