Colin McQuillan wrote:
2009/7/12 Vitor Sessak <[email protected]>:
cmcq wrote:
Author: cmcq
Date: Sun Jul 12 13:19:21 2009
New Revision: 4678
Log:
Remove incorrect comment. An FIR filter doesn't need previous output.
Modified:
amr/amr-ffmpeg.diff
Modified: amr/amr-ffmpeg.diff
==============================================================================
--- amr/amr-ffmpeg.diff Sun Jul 12 13:10:09 2009 (r4677)
+++ amr/amr-ffmpeg.diff Sun Jul 12 13:19:21 2009 (r4678)
@@ -113,3 +113,13 @@ Index: libavcodec/celp_filters.h
* LP synthesis filter.
* @param out [out] pointer to output buffer
* - the array out[-filter_length, -1] must
+@@ -101,9 +118,6 @@
+ * @param buffer_length amount of data to process
+ * @param filter_length filter length (10 for 10th order LP filter)
+ *
+- * @note Output buffer must contain filter_length samples of past
+- * speech data before pointer.
+- *
+ * Routine applies A(z) filter to given speech data.
+ */
+ void ff_celp_lp_zero_synthesis_filterf(
int i,n;
// Avoids a +1 in the inner loop.
filter_length++;
for(n=0; n<buffer_length; n++)
{
out[n] = in[n];
for(i=1; i<filter_length; i++)
out[n] -= filter_coeffs[i-1] * out[n-i];
When n==0 and i==filter_length-1, one have
out[0] -= filter_coeffs[filter_length-2] * out[-filter_length+1];
So I'd say one really need some past data in *out buffer...
-Vitor
The snippet is ff_celp_lp_synthesis_filterf. The comment is for
ff_celp_lp_zero_synthesis_filterf.
Indeed, 100l.
-Vitor
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