On 1/27/20, Robert Deibel <deibel.rob...@googlemail.com> wrote:
> Fix shaking of image when zoom is applied by the zoompan filter.
> Resolves ticket https://trac.ffmpeg.org/ticket/4298
> ---
> Fixed the style issues and modified the comment of scale_to_grid() to
> correctly specify the functionality.
>
> libavfilter/vf_zoompan.c | 82 ++++++++++++++++++++++++++++------------
> 1 file changed, 58 insertions(+), 24 deletions(-)
>
> diff --git a/libavfilter/vf_zoompan.c b/libavfilter/vf_zoompan.c
> index 59c9b19ec8..1710f1d353 100644
> --- a/libavfilter/vf_zoompan.c
> +++ b/libavfilter/vf_zoompan.c
> @@ -150,16 +150,30 @@ static int config_output(AVFilterLink *outlink)
> return 0;
> }
>
> +/**
> + * Scales n to the next number divisible by 2 * 2^log_grid_size but
> minimally n + 2 * 2^log_grid_size.
> + *
> + * Used to scale the width and height of a frame to fit with the
> subsampling grid.
> + * @param n The number to be scaled.
> + * @param log_grid_size log 2 of the gridsize.
> + * @return The next number divisible by 2 * 2^log_grid_size but minimally n
> + 2 * 2^log_grid_size
> + */
> +static int scale_to_grid(int n, uint8_t log2_grid_size)
> +{
> + return (((n + (1 << log2_grid_size) * 2) & ~((1 << log2_grid_size) -
> 1)) + 1) & ~1;;
> +}
> +
> static int output_single_frame(AVFilterContext *ctx, AVFrame *in, double
> *var_values, int i,
> double *zoom, double *dx, double *dy)
> {
> ZPContext *s = ctx->priv;
> AVFilterLink *outlink = ctx->outputs[0];
> int64_t pts = s->frame_count;
> - int k, x, y, w, h, ret = 0;
> + int k, x, y, crop_x, crop_y, w, h, crop_w, crop_h, overscaled_w,
> overscaled_h, ret = 0;
> uint8_t *input[4];
> int px[4], py[4];
> AVFrame *out;
> + double dw, dh, dx_scaled, dy_scaled;
>
> var_values[VAR_PX] = s->x;
> var_values[VAR_PY] = s->y;
> @@ -173,32 +187,38 @@ static int output_single_frame(AVFilterContext *ctx,
> AVFrame *in, double *var_va
>
> *zoom = av_clipd(*zoom, 1, 10);
> var_values[VAR_ZOOM] = *zoom;
> - w = in->width * (1.0 / *zoom);
> - h = in->height * (1.0 / *zoom);
>
> - *dx = av_expr_eval(s->x_expr, var_values, NULL);
> + w = dw = (double) in->width * (1 / *zoom);
> + h = dh = (double) in->height * (1 / *zoom);
> + crop_w = scale_to_grid(w, s->desc->log2_chroma_w);
> + crop_h = scale_to_grid(h, s->desc->log2_chroma_h);
> + overscaled_w = outlink->w + (crop_w - dw) * *zoom;
> + overscaled_h = outlink->h + (crop_h - dh) * *zoom;
>
> - x = *dx = av_clipd(*dx, 0, FFMAX(in->width - w, 0));
> - var_values[VAR_X] = *dx;
> - x &= ~((1 << s->desc->log2_chroma_w) - 1);
> + *dx = av_expr_eval(s->x_expr, var_values, NULL);
> + crop_x = ceil(av_clipd(*dx - (((double) crop_w - w) / 2.0), 0,
> FFMAX(in->width - crop_w, 0)));
> + var_values[VAR_X] = *dx = av_clipd(*dx, 0, FFMAX(in->width - w, 0));
> + crop_x &= ~((1 << s->desc->log2_chroma_w) - 1);
>
> *dy = av_expr_eval(s->y_expr, var_values, NULL);
> + crop_y = ceil(av_clipd(*dy - (((double) crop_h - h)/ 2.0), 0,
> FFMAX(in->height - crop_h, 0)));
> + var_values[VAR_Y] = *dy = av_clipd(*dy, 0, FFMAX(in->height - h, 0));
> + crop_y &= ~((1 << s->desc->log2_chroma_h) - 1);
>
> - y = *dy = av_clipd(*dy, 0, FFMAX(in->height - h, 0));
> - var_values[VAR_Y] = *dy;
> - y &= ~((1 << s->desc->log2_chroma_h) - 1);
> -
> - out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
> + out = ff_get_video_buffer(outlink, overscaled_w, overscaled_h);
This is wrong. outlink->w/h should be used always, otherwise outlink
w/h differs from frame w/h.
> if (!out) {
> ret = AVERROR(ENOMEM);
> return ret;
> }
>
> - px[1] = px[2] = AV_CEIL_RSHIFT(x, s->desc->log2_chroma_w);
> - px[0] = px[3] = x;
> + px[1] = px[2] = AV_CEIL_RSHIFT(crop_x, s->desc->log2_chroma_w);
> + px[0] = px[3] = crop_x;
>
> - py[1] = py[2] = AV_CEIL_RSHIFT(y, s->desc->log2_chroma_h);
> - py[0] = py[3] = y;
> + py[1] = py[2] = AV_CEIL_RSHIFT(crop_y, s->desc->log2_chroma_h);
> + py[0] = py[3] = crop_y;
> +
> + for (k = 0; k < 4; k++)
> + input[k] = in->data[k] + py[k] * in->linesize[k] + px[k];
>
> s->sws = sws_alloc_context();
> if (!s->sws) {
> @@ -206,21 +226,35 @@ static int output_single_frame(AVFilterContext *ctx,
> AVFrame *in, double *var_va
> goto error;
> }
>
> - for (k = 0; in->data[k]; k++)
> - input[k] = in->data[k] + py[k] * in->linesize[k] + px[k];
> -
> - av_opt_set_int(s->sws, "srcw", w, 0);
> - av_opt_set_int(s->sws, "srch", h, 0);
> + av_opt_set_int(s->sws, "srcw", crop_w, 0);
> + av_opt_set_int(s->sws, "srch", crop_h, 0);
> av_opt_set_int(s->sws, "src_format", in->format, 0);
> - av_opt_set_int(s->sws, "dstw", outlink->w, 0);
> - av_opt_set_int(s->sws, "dsth", outlink->h, 0);
> + av_opt_set_int(s->sws, "dstw", overscaled_w, 0);
> + av_opt_set_int(s->sws, "dsth", overscaled_h, 0);
> av_opt_set_int(s->sws, "dst_format", outlink->format, 0);
> av_opt_set_int(s->sws, "sws_flags", SWS_BICUBIC, 0);
>
> if ((ret = sws_init_context(s->sws, NULL, NULL)) < 0)
> goto error;
>
> - sws_scale(s->sws, (const uint8_t *const *)&input, in->linesize, 0, h,
> out->data, out->linesize);
> + sws_scale(s->sws, (const uint8_t *const *)&input, in->linesize, 0,
> crop_h, out->data, out->linesize);
> +
> + dx_scaled = ((crop_w - dw) * *zoom) / (((double) crop_w - dw) / (*dx -
> (double) crop_x));
> + x = ceil(av_clipd(dx_scaled, 0, FFMAX(overscaled_w - outlink->w, 0)));
> + x &= ~((1 << s->desc->log2_chroma_w) - 1);
> +
> + dy_scaled = ((crop_h - dh) * *zoom) / (((double) crop_h - dh) / (*dx -
> (double) crop_y));
> + y = ceil(av_clipd(dy_scaled, 0, FFMAX(overscaled_h - outlink->h, 0)));
> + y &= ~((1 << s->desc->log2_chroma_h) - 1);
> +
> + px[1] = px[2] = AV_CEIL_RSHIFT(x, s->desc->log2_chroma_w);
> + px[0] = px[3] = x;
> +
> + py[1] = py[2] = AV_CEIL_RSHIFT(y, s->desc->log2_chroma_h);
> + py[0] = py[3] = y;
> +
> + for (k = 0; k < 4; k++)
> + out->data[k] = out->data[k] + py[k] * out->linesize[k] + px[k];
>
> out->pts = pts;
> s->frame_count++;
> --
> 2.25.0
>
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