[FFmpeg-devel] [PATCH 09/18] avradio/sdrdemux: The RTLSDR DC artifact is not consistent

[Michael Niedermayer]

so we need to check every block, we cannot just check a few and
then subtract the same value

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavradio/sdr.h      |  1 -
 libavradio/sdrdemux.c | 23 +++++++++++------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/libavradio/sdr.h b/libavradio/sdr.h
index 95ff903293..13237707b3 100644
--- a/libavradio/sdr.h
+++ b/libavradio/sdr.h
@@ -202,7 +202,6 @@ typedef struct SDRContext {
     int missing_streams;
 
     int rtlsdr_fixes;
-    float rtlsdr_dc_offset;
 } SDRContext;
 
 typedef struct ModulationDescriptor {
diff --git a/libavradio/sdrdemux.c b/libavradio/sdrdemux.c
index 392fece4e9..6682768461 100644
--- a/libavradio/sdrdemux.c
+++ b/libavradio/sdrdemux.c
@@ -1705,21 +1705,20 @@ process_next_block:
         const int8_t *halfblock0 = fifo_element[0].halfblock;
         const int8_t *halfblock1 = fifo_element[1].halfblock;
         if (sdr->rtlsdr_fixes>0) {
-            if (!sdr->rtlsdr_dc_offset || !sdr->block_center_freq) {
-                int sum = 0;
-                for (i = 0; i<2*sdr->block_size; i++)
-                    sum += halfblock0[i]
-                        +  halfblock1[i];
-                sdr->rtlsdr_dc_offset = -sum / (4.0*sdr->block_size);
-                av_log(s, AV_LOG_DEBUG, "Compensating DC offset %f (this should be around -0.6)\n", sdr->rtlsdr_dc_offset);
-            }
+            int sum = 0;
+            float offset;
+            for (i = 0; i<2*sdr->block_size; i++)
+                sum += halfblock0[i]
+                    +  halfblock1[i];
+            offset = -sum / (4.0*sdr->block_size);
+            av_log(s, AV_LOG_DEBUG, "Compensating DC offset %f (this should be around -0.6)\n", offset);
             for (i = 0; i<sdr->block_size; i++) {
-                sdr->windowed_block[i].re = (halfblock0[2*i+0] + sdr->rtlsdr_dc_offset) * sdr->window[i];
-                sdr->windowed_block[i].im = (halfblock0[2*i+1] + sdr->rtlsdr_dc_offset) * sdr->window[i];
+                sdr->windowed_block[i].re = (halfblock0[2*i+0] + offset) * sdr->window[i];
+                sdr->windowed_block[i].im = (halfblock0[2*i+1] + offset) * sdr->window[i];
             }
             for (i = sdr->block_size; i<2*sdr->block_size; i++) {
-                sdr->windowed_block[i].re = (halfblock1[2*(i - sdr->block_size)+0] + sdr->rtlsdr_dc_offset) * sdr->window[i];
-                sdr->windowed_block[i].im = (halfblock1[2*(i - sdr->block_size)+1] + sdr->rtlsdr_dc_offset) * sdr->window[i];
+                sdr->windowed_block[i].re = (halfblock1[2*(i - sdr->block_size)+0] + offset) * sdr->window[i];
+                sdr->windowed_block[i].im = (halfblock1[2*(i - sdr->block_size)+1] + offset) * sdr->window[i];
             }
         } else {
             for (i = 0; i<sdr->block_size; i++) {
-- 
2.31.1