From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: [FFmpeg-devel] [PATCH 2/2] avradio/sdrdemux: Some corrections to the FM stereo side channel
Date: Fri, 14 Jul 2023 20:03:41 +0200
Message-ID: <20230714180341.2186605-2-michael@niedermayer.cc> (raw)
In-Reply-To: <20230714180341.2186605-1-michael@niedermayer.cc>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
libavradio/sdrdemux.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/libavradio/sdrdemux.c b/libavradio/sdrdemux.c
index 041775730e..5a6a9b8894 100644
--- a/libavradio/sdrdemux.c
+++ b/libavradio/sdrdemux.c
@@ -656,7 +656,7 @@ static av_always_inline void synchronous_am_demodulationN(AVComplexFloat *iblock
for (int i = 0; i<len; i++) {
AVComplexFloat c = icarrier[i];
AVComplexFloat s = iblock[i];
- float w = window[i];
+ float w = N == 2 ? 1.0 : window[i];
AVComplexFloat c2= {c.re*c.re, c.im*c.im};
float den = w/(c2.re + c2.im);
@@ -1080,8 +1080,9 @@ static int demodulate_fm(SDRContext *sdr, Station *station, AVStream *st, AVPack
newbuf[2*i+0] = (sdr->fm_iblock[i + sdr->fm_block_size_p2].re) * sdr->fm_window_p2[i + sdr->fm_block_size_p2] * scale;
if (carrier19_i >= 0) {
- q = sst->out_buf[2*i+1] + sdr->fm_iside[i ].im * sdr->fm_window_p2[i ] * scale;
- newbuf[2*i+1] = sdr->fm_iside[i + sdr->fm_block_size_p2].im * sdr->fm_window_p2[i + sdr->fm_block_size_p2] * scale;
+ //the 0.5 is because we have both sides of the spectrum for iside
+ q = sst->out_buf[2*i+1] + sdr->fm_iside[i ].im * sdr->fm_window_p2[i ] * (scale * 0.5);
+ newbuf[2*i+1] = sdr->fm_iside[i + sdr->fm_block_size_p2].im * sdr->fm_window_p2[i + sdr->fm_block_size_p2] * (scale * 0.5);
sst->out_buf[2*i+0] = m + q;
sst->out_buf[2*i+1] = m - q;
--
2.31.1
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next prev parent reply other threads:[~2023-07-14 18:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-14 18:03 [FFmpeg-devel] [PATCH 1/2] avradio/sdrdemux: avoid repeated litteral number Michael Niedermayer
2023-07-14 18:03 ` Michael Niedermayer [this message]
2023-07-15 16:59 ` Michael Niedermayer
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