[FFmpeg-devel] [PATCH] lavc/cfhd: added alpha decompanding in rgba12

[Gagandeep Singh]

On Wed, 21 Mar 2018, 22:20 Gagandeep Singh, <deepgagan231197 at gmail.com>
wrote:

> alpha decompanding curve added to post process the decoded alpha channel
> ---
>  libavcodec/cfhd.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/libavcodec/cfhd.c b/libavcodec/cfhd.c
> index fd5555834b..e35732df45 100644
> --- a/libavcodec/cfhd.c
> +++ b/libavcodec/cfhd.c
> @@ -37,6 +37,9 @@
>  #include "thread.h"
>  #include "cfhd.h"
>
> +#define ALPHA_COMPAND_DC_OFFSET 256
> +#define ALPHA_COMPAND_GAIN 9400
> +
>  enum CFHDParam {
>      ChannelCount     =  12,
>      SubbandCount     =  14,
> @@ -94,6 +97,20 @@ static inline int dequant_and_decompand(int level, int
> quantisation)
>             FFSIGN(level) * quantisation;
>  }
>
> +static inline void process_alpha(int16_t *alpha, int width)
> +{
> +    int i, channel;
> +    for (i = 0; i < width; i++) {
> +        channel   = alpha[i];
> +        channel  -= ALPHA_COMPAND_DC_OFFSET;
> +        channel <<= 3;
> +        channel  *= ALPHA_COMPAND_GAIN;
> +        channel >>= 16;
> +        channel   = av_clip_uintp2(channel, 12);
> +        alpha[i]  = channel;
> +    }
> +}
> +
>  static inline void filter(int16_t *output, ptrdiff_t out_stride,
>                            int16_t *low, ptrdiff_t low_stride,
>                            int16_t *high, ptrdiff_t high_stride,
> @@ -792,6 +809,8 @@ static int cfhd_decode(AVCodecContext *avctx, void
> *data, int *got_frame,
>          high = s->plane[plane].l_h[7];
>          for (i = 0; i < lowpass_height * 2; i++) {
>              horiz_filter_clip(dst, low, high, lowpass_width, s->bpc);
> +            if (act_plane == 3)
> +                process_alpha(dst, lowpass_width * 2);
>              low  += lowpass_width;
>              high += lowpass_width;
>              dst  += pic->linesize[act_plane] / 2;
> --
> 2.14.1
>

ticket #6265

>