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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
This commit is contained in:
Ian Braithwaite 2007-03-13 19:44:02 +00:00 committed by Benjamin Larsson
parent e057461dac
commit 85e7386ae0
1 changed files with 28 additions and 41 deletions
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69
libavcodec/cook.c
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@ -684,33 +684,6 @@ 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
*
@ -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);
}
}