[x265] Custom LowRes scale

Deepthi Nandakumar deepthi at multicorewareinc.com
Mon Jul 21 18:16:33 CEST 2014


Thanks, this is certainly an enhancement to x265 lookahead. We would be
interested in this - especially if you can also include some efficiency
(bitrate vs SSIM) metrics that describe the penalty moving from
X265_LOWRES_SCALE of 4 to higher scales.


On Mon, Jul 21, 2014 at 8:49 PM, Nicolas Morey-Chaisemartin <
nmorey at kalray.eu> wrote:

> Hi,
>
> We recently profiled x265 pre-analysis to estimate what performance we
> could reach using our accelerator and I was quite disappointed by the
> performance.
> When running on a Core-i7 with AVX at roughly 2.7GHz, we barely reached
> the 30fps mark using ultrafast preset on a 4K video.
>


> After a little bit of browsing I realized that work in LosRew is always
> done at 1/4th of the final resolution which seems fair but requires a huge
> amount of work for 4K.
> It seemed straight forward enough to change the divider at LowRes
> initialization but it seems there are a lot of hard coded values that
> depend both on the LowRes divider and the LowRes CU Size.
>
> Here's a patch (definitly not applicable like this but just to give an
> idea of where I'm going) that seems to fix most of the hard-coded value.
> It still works with a X265_LOWRES_SCALE of 4 and the perf is definilty
> improving (29fps => 40fps on a 2048x1024 medium preset on a E5504).
>
> Would you be interested in a clean version of this? At least the
> hard-coded CU_SIZE part?
> IMHO it would be better to have "dynamic" value for LowRes depending on
> preset (or equivalent) and the input resolution...
> 1/4th is fast enough in HD not to be an issue but for RT stream in 4K or
> more, 1/16 will be compulsory.
>
> Nicolas
>
> ---
>  x265/source/common/common.h          |  1 +
>  x265/source/common/lowres.cpp        |  4 ++--
>  x265/source/encoder/frameencoder.cpp |  7 ++++---
>  x265/source/encoder/ratecontrol.cpp  | 16 ++++++++--------
>  x265/source/encoder/slicetype.cpp    |  8 ++++----
>  5 files changed, 19 insertions(+), 17 deletions(-)
>
> diff --git a/x265/source/common/common.h b/x265/source/common/common.h
> index 06f60e7..00e73fc 100644
> --- a/x265/source/common/common.h
> +++ b/x265/source/common/common.h
> @@ -156,6 +156,7 @@ typedef int32_t  coeff_t;      // transform coefficient
>  // high cost estimates (intra and inter both suffer)
>  #define X265_LOWRES_CU_SIZE   8
>  #define X265_LOWRES_CU_BITS   3
> +#define X265_LOWRES_SCALE     2
>   #define X265_MALLOC(type, count)    (type*)x265_malloc(sizeof(type) *
> (count))
>  #define X265_FREE(ptr)              x265_free(ptr)
> diff --git a/x265/source/common/lowres.cpp b/x265/source/common/lowres.cpp
> index 5fc2f6b..6138023 100644
> --- a/x265/source/common/lowres.cpp
> +++ b/x265/source/common/lowres.cpp
> @@ -31,8 +31,8 @@ bool Lowres::create(TComPicYuv *orig, int _bframes, bool
> bAQEnabled)
>  {
>      isLowres = true;
>      bframes = _bframes;
> -    width = orig->getWidth() / 2;
> -    lines = orig->getHeight() / 2;
> +    width = orig->getWidth() / X265_LOWRES_SCALE;
> +    lines = orig->getHeight() / X265_LOWRES_SCALE;
>      lumaStride = width + 2 * orig->getLumaMarginX();
>      if (lumaStride & 31)
>          lumaStride += 32 - (lumaStride & 31);
> diff --git a/x265/source/encoder/frameencoder.cpp b/x265/source/encoder/
> frameencoder.cpp
> index 8c3ee26..7213f60 100644
> --- a/x265/source/encoder/frameencoder.cpp
> +++ b/x265/source/encoder/frameencoder.cpp
> @@ -1300,9 +1300,10 @@ int FrameEncoder::calcQpForCu(uint32_t cuAddr,
> double baseQp)
>       /* Derive qpOffet for each CU by averaging offsets for all 16x16
> blocks in the cu. */
>      double qp_offset = 0;
> -    int maxBlockCols = (m_frame->getPicYuvOrg()->getWidth() + (16 - 1))
> / 16;
> -    int maxBlockRows = (m_frame->getPicYuvOrg()->getHeight() + (16 - 1))
> / 16;
> -    int noOfBlocks = g_maxCUSize / 16;
> +    int lowResCu = (X265_LOWRES_CU_SIZE * X265_LOWRES_SCALE);
> +    int maxBlockCols = (m_frame->getPicYuvOrg()->getWidth() + (lowResCu
> - 1)) / lowResCu;
> +    int maxBlockRows = (m_frame->getPicYuvOrg()->getHeight() + (lowResCu
> - 1)) / lowResCu;
> +    int noOfBlocks = g_maxCUSize / lowResCu;
>      int block_y = (cuAddr / m_frame->getPicSym()->getFrameWidthInCU()) *
> noOfBlocks;
>      int block_x = (cuAddr * noOfBlocks) - block_y * m_frame->getPicSym()->
> getFrameWidthInCU();
>  diff --git a/x265/source/encoder/ratecontrol.cpp b/x265/source/encoder/
> ratecontrol.cpp
> index 4358994..5fcc27a 100644
> --- a/x265/source/encoder/ratecontrol.cpp
> +++ b/x265/source/encoder/ratecontrol.cpp
> @@ -161,8 +161,8 @@ void RateControl::calcAdaptiveQuantFrame(Frame *pic)
>      if (m_param->rc.aqMode == X265_AQ_NONE || m_param->rc.aqStrength == 0)
>      {
>          /* Need to init it anyways for CU tree */
> -        int cuWidth = ((maxCol / 2) + X265_LOWRES_CU_SIZE - 1) >>
> X265_LOWRES_CU_BITS;
> -        int cuHeight = ((maxRow / 2) + X265_LOWRES_CU_SIZE - 1) >>
> X265_LOWRES_CU_BITS;
> +        int cuWidth = ((maxCol / X265_LOWRES_SCALE) + X265_LOWRES_CU_SIZE
> - 1) >> X265_LOWRES_CU_BITS;
> +        int cuHeight = ((maxRow / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
>          int cuCount = cuWidth * cuHeight;
>           if (m_param->rc.aqMode && m_param->rc.aqStrength == 0)
> @@ -194,9 +194,9 @@ void RateControl::calcAdaptiveQuantFrame(Frame *pic)
>          if (m_param->rc.aqMode == X265_AQ_AUTO_VARIANCE)
>          {
>              double bit_depth_correction = pow(1 << (X265_DEPTH - 8), 0.5);
> -            for (block_y = 0; block_y < maxRow; block_y += 16)
> +            for (block_y = 0; block_y < maxRow; block_y +=
> (X265_LOWRES_CU_SIZE * X265_LOWRES_SCALE))
>              {
> -                for (block_x = 0; block_x < maxCol; block_x += 16)
> +                for (block_x = 0; block_x < maxCol; block_x +=
> (X265_LOWRES_CU_SIZE * X265_LOWRES_SCALE))
>                  {
>                      uint32_t energy = acEnergyCu(pic, block_x, block_y);
>                      qp_adj = pow(energy + 1, 0.1);
> @@ -216,9 +216,9 @@ void RateControl::calcAdaptiveQuantFrame(Frame *pic)
>              strength = m_param->rc.aqStrength * 1.0397f;
>           block_xy = 0;
> -        for (block_y = 0; block_y < maxRow; block_y += 16)
> +        for (block_y = 0; block_y < maxRow; block_y +=
> (X265_LOWRES_CU_SIZE * X265_LOWRES_SCALE))
>          {
> -            for (block_x = 0; block_x < maxCol; block_x += 16)
> +            for (block_x = 0; block_x < maxCol; block_x +=
>  (X265_LOWRES_CU_SIZE * X265_LOWRES_SCALE))
>              {
>                  if (m_param->rc.aqMode == X265_AQ_AUTO_VARIANCE)
>                  {
> @@ -260,8 +260,8 @@ void RateControl::calcAdaptiveQuantFrame(Frame *pic)
>  RateControl::RateControl(x265_param *p)
>  {
>      m_param = p;
> -    int lowresCuWidth = ((m_param->sourceWidth / 2) + X265_LOWRES_CU_SIZE
> - 1) >> X265_LOWRES_CU_BITS;
> -    int lowresCuHeight = ((m_param->sourceHeight / 2)  +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
> +    int lowresCuWidth = ((m_param->sourceWidth / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
> +    int lowresCuHeight = ((m_param->sourceHeight / X265_LOWRES_SCALE)  +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
>      m_ncu = lowresCuWidth * lowresCuHeight;
>       if (m_param->rc.cuTree)
> diff --git a/x265/source/encoder/slicetype.cpp b/x265/source/encoder/
> slicetype.cpp
> index 34d0b3b..4a2f2cb 100644
> --- a/x265/source/encoder/slicetype.cpp
> +++ b/x265/source/encoder/slicetype.cpp
> @@ -65,8 +65,8 @@ Lookahead::Lookahead(x265_param *param, ThreadPool*
> pool)
>      m_lastNonB = NULL;
>      m_bFilling = true;
>      m_bFlushed = false;
> -    m_widthInCU = ((m_param->sourceWidth / 2) + X265_LOWRES_CU_SIZE - 1)
> >> X265_LOWRES_CU_BITS;
> -    m_heightInCU = ((m_param->sourceHeight / 2) + X265_LOWRES_CU_SIZE -
> 1) >> X265_LOWRES_CU_BITS;
> +    m_widthInCU = ((m_param->sourceWidth / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
> +    m_heightInCU = ((m_param->sourceHeight / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
>      m_scratch = (int*)x265_malloc(m_widthInCU * sizeof(int));
>      memset(m_histogram, 0, sizeof(m_histogram));
>  }
> @@ -1201,8 +1201,8 @@ CostEstimate::~CostEstimate()
>  void CostEstimate::init(x265_param *_param, Frame *pic)
>  {
>      m_param = _param;
> -    m_widthInCU = ((m_param->sourceWidth / 2) + X265_LOWRES_CU_SIZE - 1)
> >> X265_LOWRES_CU_BITS;
> -    m_heightInCU = ((m_param->sourceHeight / 2) + X265_LOWRES_CU_SIZE -
> 1) >> X265_LOWRES_CU_BITS;
> +    m_widthInCU = ((m_param->sourceWidth / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
> +    m_heightInCU = ((m_param->sourceHeight / X265_LOWRES_SCALE) +
> X265_LOWRES_CU_SIZE - 1) >> X265_LOWRES_CU_BITS;
>       m_rows = new EstimateRow[m_heightInCU];
>      for (int i = 0; i < m_heightInCU; i++)
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