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Commit aea2715e authored by Jean-Michel Trivi's avatar Jean-Michel Trivi
Browse files

Prevent occurences of clipping in loud downmixed scenes 

The downmixer effect is a mixer, wich, like the platform mixer,
  hard-clips. To prevent clipping during loud scenes across multiple
  chanels, apply a fixed attenuation on the result of the downmix.
  Note that this attenuation is lower the theoretical required
  attenuation (except for quad and surround) but is adequate for
  most content.

Bug 4280902
Change-Id: Iec520e9f1367284d6102633f532429361717692d
parent e737cda6

media/libeffects/downmix/EffectDownmix.c

+20 −20
Original line number Diff line number Diff line
@@ -822,9 +822,9 @@ void Downmix_foldFromQuad(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool ac 
    if (accumulate) {

        while (numFrames) {

            // FL + RL

            pDst[0] = clamp16(pDst[0] + pSrc[0] + pSrc[2]);

            pDst[0] = clamp16(pDst[0] + ((pSrc[0] + pSrc[2]) >> 1));

            // FR + RR

            pDst[1] = clamp16(pDst[1] + pSrc[1] + pSrc[3]);

            pDst[1] = clamp16(pDst[1] + ((pSrc[1] + pSrc[3]) >> 1));

            pSrc += 4;

            pDst += 2;

            numFrames--;
@@ -832,9 +832,9 @@ void Downmix_foldFromQuad(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool ac 
    } else { // same code as above but without adding and clamping pDst[i] to itself

        while (numFrames) {

            // FL + RL

            pDst[0] = clamp16(pSrc[0] + pSrc[2]);

            pDst[0] = clamp16((pSrc[0] + pSrc[2]) >> 1);

            // FR + RR

            pDst[1] = clamp16(pSrc[1] + pSrc[3]);

            pDst[1] = clamp16((pSrc[1] + pSrc[3]) >> 1);

            pSrc += 4;

            pDst += 2;

            numFrames--;
@@ -877,8 +877,8 @@ void Downmix_foldFromSurround(int16_t *pSrc, int16_t*pDst, size_t numFrames, boo 
            // FR + centerPlusRearContrib

            rt = (pSrc[1] << 12) + centerPlusRearContrib;

            // accumulate in destination

            pDst[0] = clamp16(pDst[0] + (lt >> 12));

            pDst[1] = clamp16(pDst[1] + (rt >> 12));

            pDst[0] = clamp16(pDst[0] + (lt >> 13));

            pDst[1] = clamp16(pDst[1] + (rt >> 13));

            pSrc += 4;

            pDst += 2;

            numFrames--;
@@ -892,8 +892,8 @@ void Downmix_foldFromSurround(int16_t *pSrc, int16_t*pDst, size_t numFrames, boo 
            // FR + centerPlusRearContrib

            rt = (pSrc[1] << 12) + centerPlusRearContrib;

            // store in destination

            pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above

            pDst[0] = clamp16(lt >> 13); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 13); // differs from when accumulate is true above

            pSrc += 4;

            pDst += 2;

            numFrames--;
@@ -939,8 +939,8 @@ void Downmix_foldFrom5Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool 
            // FR + centerPlusLfeContrib + RR

            rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[5] << 12);

            // accumulate in destination

            pDst[0] = clamp16(pDst[0] + (lt >> 12));

            pDst[1] = clamp16(pDst[1] + (rt >> 12));

            pDst[0] = clamp16(pDst[0] + (lt >> 13));

            pDst[1] = clamp16(pDst[1] + (rt >> 13));

            pSrc += 6;

            pDst += 2;

            numFrames--;
@@ -955,8 +955,8 @@ void Downmix_foldFrom5Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool 
            // FR + centerPlusLfeContrib + RR

            rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[5] << 12);

            // store in destination

            pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above

            pDst[0] = clamp16(lt >> 13); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 13); // differs from when accumulate is true above

            pSrc += 6;

            pDst += 2;

            numFrames--;
@@ -1004,8 +1004,8 @@ void Downmix_foldFrom7Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool 
            // FR + centerPlusLfeContrib + SR + RR

            rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[7] << 12) + (pSrc[5] << 12);

            //accumulate in destination

            pDst[0] = clamp16(pDst[0] + (lt >> 12));

            pDst[1] = clamp16(pDst[1] + (rt >> 12));

            pDst[0] = clamp16(pDst[0] + (lt >> 13));

            pDst[1] = clamp16(pDst[1] + (rt >> 13));

            pSrc += 8;

            pDst += 2;

            numFrames--;
@@ -1020,8 +1020,8 @@ void Downmix_foldFrom7Point1(int16_t *pSrc, int16_t*pDst, size_t numFrames, bool 
            // FR + centerPlusLfeContrib + SR + RR

            rt = (pSrc[1] << 12) + centerPlusLfeContrib + (pSrc[7] << 12) + (pSrc[5] << 12);

            // store in destination

            pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above

            pDst[0] = clamp16(lt >> 13); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 13); // differs from when accumulate is true above

            pSrc += 8;

            pDst += 2;

            numFrames--;
@@ -1130,8 +1130,8 @@ bool Downmix_foldGeneric( 
            lt += centersLfeContrib;

            rt += centersLfeContrib;

            // accumulate in destination

            pDst[0] = clamp16(pDst[0] + (lt >> 12));

            pDst[1] = clamp16(pDst[1] + (rt >> 12));

            pDst[0] = clamp16(pDst[0] + (lt >> 13));

            pDst[1] = clamp16(pDst[1] + (rt >> 13));

            pSrc += numChan;

            pDst += 2;

            numFrames--;
@@ -1159,8 +1159,8 @@ bool Downmix_foldGeneric( 
            lt += centersLfeContrib;

            rt += centersLfeContrib;

            // store in destination

            pDst[0] = clamp16(lt >> 12); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 12); // differs from when accumulate is true above

            pDst[0] = clamp16(lt >> 13); // differs from when accumulate is true above

            pDst[1] = clamp16(rt >> 13); // differs from when accumulate is true above

            pSrc += numChan;

            pDst += 2;

            numFrames--;