[FFmpeg-cvslog] Implement lms_update()

[Mashiat Sarker Shakkhar]

ffmpeg | branch: master | Mashiat Sarker Shakkhar <shahriman_ams at yahoo.com> | Sun Nov  6 03:02:41 2011 +0600| [269a0dee191183582bd32ab9c64acf6943176e06] | committer: Mashiat Sarker Shakkhar

Implement lms_update()

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=269a0dee191183582bd32ab9c64acf6943176e06
---

 libavcodec/wmalosslessdec.c |   49 +++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/libavcodec/wmalosslessdec.c b/libavcodec/wmalosslessdec.c
index eafe145..c95a863 100644
--- a/libavcodec/wmalosslessdec.c
+++ b/libavcodec/wmalosslessdec.c
@@ -771,6 +771,55 @@ static int lms_predict(WmallDecodeCtx *s, int ich, int ilms)
     return pred;
 }
 
+static void lms_update(WmallDecodeCtx *s, int ich, int ilms, int32_t input, int32_t pred)
+{
+    int icoef;
+    int recent = s->cdlms[ich][ilms].recent;
+    int range = 1 << (s->bits_per_sample - 1);
+    int bps = s->bits_per_sample > 16 ? 4 : 2; // bytes per sample
+
+    if (input > pred) {
+        for (icoef = 0; icoef < s->cdlms[ich][ilms].order; icoef++)
+            s->cdlms[ich][ilms].coefs[icoef] +=
+                s->cdlms[ich][ilms].lms_updates[icoef + recent];
+    } else {
+        for (icoef = 0; icoef < s->cdlms[ich][ilms].order; icoef++)
+            s->cdlms[ich][ilms].coefs[icoef] -=
+                s->cdlms[ich][ilms].lms_updates[icoef];     // XXX: [icoef + recent] ?
+    }
+    s->cdlms[ich][ilms].recent--;
+    s->cdlms[ich][ilms].lms_prevvalues[recent] = av_clip(input, -range, range - 1);
+
+    if (input > pred)
+        s->cdlms[ich][ilms].lms_updates[recent] = s->update_speed[ich];
+    else if (input < pred)
+        s->cdlms[ich][ilms].lms_updates[recent] = -s->update_speed[ich];
+
+    /* XXX: spec says:
+    cdlms[iCh][ilms].updates[iRecent + cdlms[iCh][ilms].order >> 4] >>= 2;
+    lms_updates[iCh][ilms][iRecent + cdlms[iCh][ilms].order >> 3] >>= 1;
+
+        Questions is - are cdlms[iCh][ilms].updates[] and lms_updates[][][] two
+        seperate buffers? Here I've assumed that the two are same which makes
+        more sense to me.
+    */
+    s->cdlms[ich][ilms].lms_updates[recent + s->cdlms[ich][ilms].order >> 4] >>= 2;
+    s->cdlms[ich][ilms].lms_updates[recent + s->cdlms[ich][ilms].order >> 3] >>= 1;
+    /* XXX: recent + (s->cdlms[ich][ilms].order >> 4) ? */
+
+    if (s->cdlms[ich][ilms].recent == 0) {
+        /* XXX: This memcpy()s will probably fail if a fixed 32-bit buffer is used.
+                follow kshishkov's suggestion of using a union. */
+        memcpy(s->cdlms[ich][ilms].lms_prevvalues + s->cdlms[ich][ilms].order,
+               s->cdlms[ich][ilms].lms_prevvalues,
+               bps * s->cdlms[ich][ilms].order);
+        memcpy(s->cdlms[ich][ilms].lms_updates + s->cdlms[ich][ilms].order,
+               s->cdlms[ich][ilms].lms_updates,
+               bps * s->cdlms[ich][ilms].order);
+        s->cdlms[ich][ilms].recent = s->cdlms[ich][ilms].order;
+    }
+}
+
 /**
  *@brief Decode a single subframe (block).
  *@param s codec context