[FFmpeg-devel] [PATCH] vf_tinterlace: add vertical low-pass-filter option to mode 4 and 5
Stefano Sabatini
stefasab at gmail.com
Sat Dec 22 13:10:08 CET 2012
On date Friday 2012-12-21 12:58:07 +0000, Mark Himsley encoded:
> On 19/12/2012 17:17, Mark Himsley wrote:
> > Low-pass filtering is required when creating an interlaced destination
> > from a progressive source which contains high-frequency vertical detail.
> > Filtering will reduce interlace 'twitter' and Moire patterning.
>
> minor update to correct the consts.
Sorry for the slow reply.
>
> --
> Mark
> diff --git a/doc/filters.texi b/doc/filters.texi
> index a2b4fbe..0198f9a 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -3900,9 +3900,28 @@ Perform various types of temporal field interlacing.
> Frames are counted starting from 1, so the first input frame is
> considered odd.
>
> -This filter accepts a single option @option{mode} specifying the mode,
> -which can be specified either by specyfing @code{mode=VALUE} either
> -specifying the value alone. Available values are:
> +This filter accepts upto two options in the form of @var{key}=@var{value}
> +pairs separated by ":".
> +Alternatively, the @var{mode} option can be specified as a value alone,
> +optionally followed by a ":" and a @var{key}=@var{value} option.
> +
> +A description of the accepted options follows.
> +
> + at table @option
> +
> + at item mode
> +Specifies the mode of the interlacing. This option can also be
> +specified as a value alone. See below for a list of values for this option.
> +
> + at item filter
> +Specifies whether a vertical low-pass filtering will be applied.
> +The default value is @code{0}, meaning no filtering will be applied.
> +The value of @code{1} will enable vertical low-pass filtering for
> + at var{mode} @code{4} and @code{5}.
As an alternative we might consider adding flags=+low_pass_filter
> +
> + at end table
> +
> +Available values for @var{mode} are:
>
> @table @samp
> @item merge, 0
> diff --git a/libavfilter/vf_tinterlace.c b/libavfilter/vf_tinterlace.c
> index 843a66c..df88674 100644
> --- a/libavfilter/vf_tinterlace.c
> +++ b/libavfilter/vf_tinterlace.c
> @@ -45,6 +45,7 @@ enum TInterlaceMode {
> typedef struct {
> const AVClass *class;
> enum TInterlaceMode mode; ///< interlace mode selected
> + int filter; ///< interlace filtering enabled
> int frame; ///< number of the output frame
> int vsub; ///< chroma vertical subsampling
> AVFilterBufferRef *cur;
> @@ -65,6 +66,7 @@ static const AVOption tinterlace_options[] = {
> {"interleave_top", "interleave top and bottom fields", 0, AV_OPT_TYPE_CONST, {.i64=MODE_INTERLEAVE_TOP}, INT_MIN, INT_MAX, FLAGS, "mode"},
> {"interleave_bottom", "interleave bottom and top fields", 0, AV_OPT_TYPE_CONST, {.i64=MODE_INTERLEAVE_BOTTOM}, INT_MIN, INT_MAX, FLAGS, "mode"},
> {"interlacex2", "interlace fields from two consecutive frames", 0, AV_OPT_TYPE_CONST, {.i64=MODE_INTERLACEX2}, INT_MIN, INT_MAX, FLAGS, "mode"},
> + {"filter", "enable interlace filtering", OFFSET(filter), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, FLAGS, "filter"},
>
> {NULL}
> };
> @@ -142,8 +144,13 @@ static int config_out_props(AVFilterLink *outlink)
> tinterlace->black_linesize[i] * h);
> }
> }
> - av_log(ctx, AV_LOG_VERBOSE, "mode:%d h:%d -> h:%d\n",
> - tinterlace->mode, inlink->h, outlink->h);
> + if (tinterlace->filter && !(tinterlace->mode == MODE_INTERLEAVE_TOP
> + || tinterlace->mode == MODE_INTERLEAVE_BOTTOM)) {
> + av_log(ctx, AV_LOG_WARNING, "filter not required for mode:%d\n", tinterlace->mode);
> + tinterlace->filter = 0;
> + }
> + av_log(ctx, AV_LOG_VERBOSE, "mode:%d filter:%s h:%d -> h:%d\n",
> + tinterlace->mode, tinterlace->filter ? "on" : "off", inlink->h, outlink->h);
>
> return 0;
> }
> @@ -189,6 +196,66 @@ void copy_picture_field(uint8_t *dst[4], int dst_linesize[4],
> }
> }
>
> +/**
> + * Copy with low-pass filter picture field from src to dst.
> + * Low-pass filtering is required when creating an interlaced destination from
> + * a progressive source which contains high-frequency vertical detail.
> + * Filtering will reduce interlace 'twitter' and Moiré patterning.
Note: this may be moved to user docs.
> + * Other than low-pass filtering, this functions identicaly to
> + * copy_picture_field() above.
Note: would it make sense to move this to a separate filter?
> + *
> + * @param src_field copy from upper, lower field or both
> + * @param interleave leave a padding line between each copied line
> + * @param dst_field copy to upper or lower field,
> + * only meaningful when interleave is selected
> + */
> +static inline
> +void filter_copy_picture_field(uint8_t *dst[4], int dst_linesize[4],
> + const uint8_t *src[4], int src_linesize[4],
> + enum AVPixelFormat format, int w, int src_h,
> + int src_field, int interleave, int dst_field)
> +{
> + const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
> + int plane, vsub = desc->log2_chroma_h;
> + int k = src_field == FIELD_UPPER_AND_LOWER ? 1 : 2;
> +
> + for (plane = 0; plane < desc->nb_components; plane++) {
> + int lines = plane == 1 || plane == 2 ? src_h >> vsub : src_h;
> + int linesize = av_image_get_linesize(format, w, plane);
> + uint8_t *dstp = dst[plane];
> + const uint8_t *srcp = src[plane];
> + int srcp_linesize;
> + int dstp_linesize;
> +
> + if (linesize < 0)
> + return;
> +
> + lines /= k;
> + if (src_field == FIELD_LOWER)
> + srcp += src_linesize[plane];
> + if (interleave && dst_field == FIELD_LOWER)
> + dstp += dst_linesize[plane];
> +
> + srcp_linesize = src_linesize[plane] * k;
> + dstp_linesize = dst_linesize[plane] * (interleave ? 2 : 1);
> +
> + for (int h = lines; h > 0; h--) {
> + const uint8_t *srcp_above = srcp - src_linesize[plane];
> + const uint8_t *srcp_below = srcp + src_linesize[plane];
> + if (h == lines) srcp_above = srcp; // there is no line above
> + if (h == 1) srcp_below = srcp; // there is no line below
> + for (int i = 0; i < linesize; i++) {
> + // this calculation is an integer representation of
> + // '0.5 * current + 0.25 * above + 0.25 + below'
> + // '1 +' is for rounding
> + dstp[i] = (1 + srcp[i] + srcp[i] + srcp_above[i] + srcp_below[i]) >> 2;
> + }
> + dstp += dstp_linesize;
> + srcp += srcp_linesize;
> + }
> + }
> +}
> +
> static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
> {
> AVFilterContext *ctx = inlink->dst;
> @@ -267,17 +334,29 @@ static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
> avfilter_copy_buffer_ref_props(out, cur);
> out->video->interlaced = 1;
> out->video->top_field_first = tff;
> -
> - /* copy upper/lower field from cur */
> - copy_picture_field(out->data, out->linesize,
> - (const uint8_t **)cur->data, cur->linesize,
> - inlink->format, inlink->w, inlink->h,
> - tff ? FIELD_UPPER : FIELD_LOWER, 1, tff ? FIELD_UPPER : FIELD_LOWER);
> - /* copy lower/upper field from next */
> - copy_picture_field(out->data, out->linesize,
> - (const uint8_t **)next->data, next->linesize,
> - inlink->format, inlink->w, inlink->h,
> - tff ? FIELD_LOWER : FIELD_UPPER, 1, tff ? FIELD_LOWER : FIELD_UPPER);
> + if (tinterlace->filter) {
> + /* copy upper/lower field from cur */
> + filter_copy_picture_field(out->data, out->linesize,
> + (const uint8_t **)cur->data, cur->linesize,
> + inlink->format, inlink->w, inlink->h,
> + tff ? FIELD_UPPER : FIELD_LOWER, 1, tff ? FIELD_UPPER : FIELD_LOWER);
> + /* copy lower/upper field from next */
> + filter_copy_picture_field(out->data, out->linesize,
> + (const uint8_t **)next->data, next->linesize,
> + inlink->format, inlink->w, inlink->h,
> + tff ? FIELD_LOWER : FIELD_UPPER, 1, tff ? FIELD_LOWER : FIELD_UPPER);
> + } else {
> + /* copy upper/lower field from cur */
> + copy_picture_field(out->data, out->linesize,
> + (const uint8_t **)cur->data, cur->linesize,
> + inlink->format, inlink->w, inlink->h,
> + tff ? FIELD_UPPER : FIELD_LOWER, 1, tff ? FIELD_UPPER : FIELD_LOWER);
> + /* copy lower/upper field from next */
> + copy_picture_field(out->data, out->linesize,
> + (const uint8_t **)next->data, next->linesize,
> + inlink->format, inlink->w, inlink->h,
> + tff ? FIELD_LOWER : FIELD_UPPER, 1, tff ? FIELD_LOWER : FIELD_UPPER);
> + }
simpler: add a parameter to copy_picture_field so you avoid
duplication here.
--
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