It looks like there is some extra data carried to enhance sampling
results. When you tune to some some weak/empty channel those bits
are always zeroes. When you tune to some channel where is very
strong signals those bits are all zeroes.
Examining those 32-bits reveals shortly there is 16 pieces of 2-bit
numbers. Number seen are 0, 1 and 3 - for some reason 2 is not used.
I used that number to shift bits given amount to left, "increasing"
sampling resolution by 3-bits. It may be wrong, but after some testing
it still provides better signal.
Signed-off-by: Antti Palosaari <crope@xxxxxx>
---
drivers/staging/media/msi3101/sdr-msi3101.c | 120 ++++++++++++++++------------
1 file changed, 67 insertions(+), 53 deletions(-)
diff --git a/drivers/staging/media/msi3101/sdr-msi3101.c b/drivers/staging/media/msi3101/sdr-msi3101.c
index b6a8939..c73f1d9 100644
--- a/drivers/staging/media/msi3101/sdr-msi3101.c
+++ b/drivers/staging/media/msi3101/sdr-msi3101.c
@@ -409,6 +409,7 @@ struct msi3101_state {
u32 next_sample; /* for track lost packets */
u32 sample; /* for sample rate calc */
unsigned long jiffies;
+ unsigned int sample_ctrl_bit[4];
};
/* Private functions */
@@ -430,6 +431,51 @@ leave:
}
/*
+ * +===========================================================================
+ * | 00-1024 | USB packet
+ * +===========================================================================
+ * | 00- 03 | sequence number of first sample in that USB packet
+ * +---------------------------------------------------------------------------
+ * | 04- 15 | garbage
+ * +---------------------------------------------------------------------------
+ * | 16- 175 | samples
+ * +---------------------------------------------------------------------------
+ * | 176- 179 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 180- 339 | samples
+ * +---------------------------------------------------------------------------
+ * | 340- 343 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 344- 503 | samples
+ * +---------------------------------------------------------------------------
+ * | 504- 507 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 508- 667 | samples
+ * +---------------------------------------------------------------------------
+ * | 668- 671 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 672- 831 | samples
+ * +---------------------------------------------------------------------------
+ * | 832- 835 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 836- 995 | samples
+ * +---------------------------------------------------------------------------
+ * | 996- 999 | control bits for previous samples
+ * +---------------------------------------------------------------------------
+ * | 1000-1024 | garbage
+ * +---------------------------------------------------------------------------
+ *
+ * Bytes 4 - 7 could have some meaning?
+ *
+ * Control bits for previous samples is 32-bit field, containing 16 x 2-bit
+ * numbers. This results one 2-bit number for 8 samples. It is likely used for
+ * for bit shifting sample by given bits, increasing actual sampling resolution.
+ * Number 2 (0b10) was never seen.
+ *
+ * 6 * 16 * 2 * 4 = 768 samples. 768 * 4 = 3072 bytes
+ */
+
+/*
* Converts signed 10-bit integer into 32-bit IEEE floating point
* representation.
* Will be exact from 0 to 2^24. Above that, we round towards zero
@@ -438,20 +484,24 @@ leave:
*/
#define I2F_FRAC_BITS 23
#define I2F_MASK ((1 << I2F_FRAC_BITS) - 1)
-static uint32_t msi3101_int2float(uint32_t x)
+static u32 msi3101_convert_sample(struct msi3101_state *s, u16 x, int shift)
{
- uint32_t msb, exponent, fraction, sign;
+ u32 msb, exponent, fraction, sign;
+ s->sample_ctrl_bit[shift]++;
/* Zero is special */
if (!x)
return 0;
- /* Negative / positive value */
- if (x & 0x200) {
+ /* Convert 10-bit two's complement to 13-bit */
+ if (x & (1 << 9)) {
+ x |= ~0U << 10; /* set all the rest bits to one */
+ x <<= shift;
x = -x;
- x &= 0x3ff;
+ x &= 0xfff; /* result is 12 bit ... + sign */
sign = 1 << 31;
} else {
+ x <<= shift;
sign = 0 << 31;
}
@@ -476,6 +526,7 @@ static int msi3101_convert_stream(struct msi3101_state *s, u32 *dst,
{
int i, j, k, l, i_max, dst_len = 0;
u16 sample[4];
+ u32 bits;
#ifdef MSI3101_EXTENSIVE_DEBUG
u32 sample_num[3];
#endif
@@ -493,6 +544,7 @@ static int msi3101_convert_stream(struct msi3101_state *s, u32 *dst,
#endif
src += 16;
for (j = 0; j < 6; j++) {
+ bits = src[160 + 3] << 24 | src[160 + 2] << 16 | src[160 + 1] << 8 | src[160 + 0] << 0;
for (k = 0; k < 16; k++) {
for (l = 0; l < 10; l += 5) {
sample[0] = (src[l + 0] & 0xff) >> 0 | (src[l + 1] & 0x03) << 8;
@@ -500,10 +552,10 @@ static int msi3101_convert_stream(struct msi3101_state *s, u32 *dst,
sample[2] = (src[l + 2] & 0xf0) >> 4 | (src[l + 3] & 0x3f) << 4;
sample[3] = (src[l + 3] & 0xc0) >> 6 | (src[l + 4] & 0xff) << 2;
- *dst++ = msi3101_int2float(sample[0]);
- *dst++ = msi3101_int2float(sample[1]);
- *dst++ = msi3101_int2float(sample[2]);
- *dst++ = msi3101_int2float(sample[3]);
+ *dst++ = msi3101_convert_sample(s, sample[0], (bits >> (2 * k)) & 0x3);
+ *dst++ = msi3101_convert_sample(s, sample[1], (bits >> (2 * k)) & 0x3);
+ *dst++ = msi3101_convert_sample(s, sample[2], (bits >> (2 * k)) & 0x3);
+ *dst++ = msi3101_convert_sample(s, sample[3], (bits >> (2 * k)) & 0x3);
/* 4 x 32bit float samples */
dst_len += 4 * 4;
@@ -511,9 +563,8 @@ static int msi3101_convert_stream(struct msi3101_state *s, u32 *dst,
src += 10;
}
#ifdef MSI3101_EXTENSIVE_DEBUG
- if (memcmp(src, "\xff\xff\xff\xff", 4) && memcmp(src, "\x00\x00\x00\x00", 4))
- dev_dbg_ratelimited(&s->udev->dev,
- "padding %*ph\n", 4, src);
+ dev_dbg_ratelimited(&s->udev->dev,
+ "sample control bits %08x\n", bits);
#endif
src += 4;
}
@@ -529,9 +580,11 @@ static int msi3101_convert_stream(struct msi3101_state *s, u32 *dst,
s->jiffies = jiffies_now;
s->sample = sample_num[i_max - 1];
dev_dbg(&s->udev->dev,
- "slen=%d samples=%u msecs=%lu sampling rate=%lu\n",
+ "slen=%d samples=%u msecs=%lu sampling rate=%lu bits=%d.%d.%d.%d\n",
src_len, samples, msecs,
- samples * 1000UL / msecs);
+ samples * 1000UL / msecs,
+ s->sample_ctrl_bit[0], s->sample_ctrl_bit[1],
+ s->sample_ctrl_bit[2], s->sample_ctrl_bit[3]);
}
/* next sample (sample = sample + i * 384) */
@@ -833,45 +886,6 @@ static int msi3101_buf_prepare(struct vb2_buffer *vb)
return 0;
}
-/*
- * +===========================================================================
- * | 00-1024 | USB packet
- * +===========================================================================
- * | 00- 03 | packet address
- * +---------------------------------------------------------------------------
- * | 04- 15 | garbage
- * +---------------------------------------------------------------------------
- * | 16- 175 | samples
- * +---------------------------------------------------------------------------
- * | 176- 179 | padding
- * +---------------------------------------------------------------------------
- * | 180- 339 | samples
- * +---------------------------------------------------------------------------
- * | 340- 343 | padding
- * +---------------------------------------------------------------------------
- * | 344- 503 | samples
- * +---------------------------------------------------------------------------
- * | 504- 507 | padding
- * +---------------------------------------------------------------------------
- * | 508- 667 | samples
- * +---------------------------------------------------------------------------
- * | 668- 671 | padding
- * +---------------------------------------------------------------------------
- * | 672- 831 | samples
- * +---------------------------------------------------------------------------
- * | 832- 835 | padding
- * +---------------------------------------------------------------------------
- * | 836- 995 | samples
- * +---------------------------------------------------------------------------
- * | 996- 999 | padding
- * +---------------------------------------------------------------------------
- * | 1000-1024 | garbage
- * +---------------------------------------------------------------------------
- *
- * bytes 4 - 7 could have some meaning?
- * padding is "00 00 00 00" or "ff ff ff ff"
- * 6 * 16 * 2 * 4 = 768 samples. 768 * 4 = 3072 bytes
- */
#ifdef MSI3101_CONVERT_IN_URB_HANDLER
static int msi3101_buf_finish(struct vb2_buffer *vb)
{
--
1.7.11.7
--
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