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* This file is part of Libav.
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* Libav is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License along
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* with Libav; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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* progressive to interlaced content filter, inspired by heavy debugging of tinterlace filter
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#include "libavutil/common.h"
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#include "libavutil/opt.h"
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#include "libavutil/imgutils.h"
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#include "libavutil/avassert.h"
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enum ScanMode scan; // top or bottom field first scanning
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int lowpass; // enable or disable low pass filterning
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AVFrame *cur, *next; // the two frames from which the new one is obtained
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int got_output; // signal an output frame is reday to request_frame()
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#define OFFSET(x) offsetof(InterlaceContext, x)
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#define V AV_OPT_FLAG_VIDEO_PARAM
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static const AVOption options[] = {
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{ "scan", "scanning mode", OFFSET(scan),
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AV_OPT_TYPE_INT, {.i64 = MODE_TFF }, 0, 1, .flags = V, .unit = "scan" },
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{ "tff", "top field first", 0,
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AV_OPT_TYPE_CONST, {.i64 = MODE_TFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
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{ "bff", "bottom field first", 0,
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AV_OPT_TYPE_CONST, {.i64 = MODE_BFF }, INT_MIN, INT_MAX, .flags = V, .unit = "scan" },
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{ "lowpass", "enable vertical low-pass filter", OFFSET(lowpass),
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AV_OPT_TYPE_INT, {.i64 = 1 }, 0, 1, .flags = V },
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static const AVClass class = {
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.class_name = "interlace filter",
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.item_name = av_default_item_name,
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.version = LIBAVUTIL_VERSION_INT,
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static const enum AVPixelFormat formats_supported[] = {
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AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV444P,
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AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUVA420P,
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AV_PIX_FMT_GRAY8, AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P,
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AV_PIX_FMT_YUVJ444P, AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_NONE
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static int query_formats(AVFilterContext *ctx)
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ff_set_common_formats(ctx, ff_make_format_list(formats_supported));
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static av_cold void uninit(AVFilterContext *ctx)
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InterlaceContext *s = ctx->priv;
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av_frame_free(&s->cur);
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av_frame_free(&s->next);
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static int config_out_props(AVFilterLink *outlink)
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AVFilterContext *ctx = outlink->src;
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AVFilterLink *inlink = outlink->src->inputs[0];
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InterlaceContext *s = ctx->priv;
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av_log(ctx, AV_LOG_ERROR, "input video height is too small\n");
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return AVERROR_INVALIDDATA;
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outlink->w = inlink->w;
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outlink->h = inlink->h;
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outlink->time_base = inlink->time_base;
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outlink->time_base.num *= 2;
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av_log(ctx, AV_LOG_VERBOSE, "%s interlacing %s lowpass filter\n",
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s->scan == MODE_TFF ? "tff" : "bff", (s->lowpass) ? "with" : "without");
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static void copy_picture_field(AVFrame *src_frame, AVFrame *dst_frame,
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AVFilterLink *inlink, enum FieldType field_type,
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const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
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int vsub = desc->log2_chroma_h;
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for (plane = 0; plane < desc->nb_components; plane++) {
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int lines = (plane == 1 || plane == 2) ? -(-inlink->h) >> vsub : inlink->h;
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int linesize = av_image_get_linesize(inlink->format, inlink->w, plane);
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uint8_t *dstp = dst_frame->data[plane];
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const uint8_t *srcp = src_frame->data[plane];
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av_assert0(linesize >= 0);
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lines = (lines + (field_type == FIELD_UPPER)) / 2;
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if (field_type == FIELD_LOWER)
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srcp += src_frame->linesize[plane];
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if (field_type == FIELD_LOWER)
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dstp += dst_frame->linesize[plane];
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int srcp_linesize = src_frame->linesize[plane] * 2;
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int dstp_linesize = dst_frame->linesize[plane] * 2;
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for (j = lines; j > 0; j--) {
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const uint8_t *srcp_above = srcp - src_frame->linesize[plane];
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const uint8_t *srcp_below = srcp + src_frame->linesize[plane];
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srcp_above = srcp; // there is no line above
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srcp_below = srcp; // there is no line below
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for (i = 0; i < linesize; i++) {
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// this calculation is an integer representation of
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// '0.5 * current + 0.25 * above + 0.25 * below'
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// '1 +' is for rounding.
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dstp[i] = (1 + srcp[i] + srcp[i] + srcp_above[i] + srcp_below[i]) >> 2;
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dstp += dstp_linesize;
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srcp += srcp_linesize;
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av_image_copy_plane(dstp, dst_frame->linesize[plane] * 2,
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srcp, src_frame->linesize[plane] * 2,
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static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
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AVFilterContext *ctx = inlink->dst;
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AVFilterLink *outlink = ctx->outputs[0];
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InterlaceContext *s = ctx->priv;
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av_frame_free(&s->cur);
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/* we need at least two frames */
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if (!s->cur || !s->next)
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if (s->cur->interlaced_frame) {
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av_log(ctx, AV_LOG_WARNING,
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"video is already interlaced, adjusting framerate only\n");
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out = av_frame_clone(s->cur);
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return AVERROR(ENOMEM);
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out->pts /= 2; // adjust pts to new framerate
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ret = ff_filter_frame(outlink, out);
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tff = (s->scan == MODE_TFF);
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out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
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return AVERROR(ENOMEM);
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av_frame_copy_props(out, s->cur);
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out->interlaced_frame = 1;
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out->top_field_first = tff;
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out->pts /= 2; // adjust pts to new framerate
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/* copy upper/lower field from cur */
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copy_picture_field(s->cur, out, inlink, tff ? FIELD_UPPER : FIELD_LOWER, s->lowpass);
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av_frame_free(&s->cur);
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/* copy lower/upper field from next */
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copy_picture_field(s->next, out, inlink, tff ? FIELD_LOWER : FIELD_UPPER, s->lowpass);
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av_frame_free(&s->next);
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ret = ff_filter_frame(outlink, out);
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static int request_frame(AVFilterLink *outlink)
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AVFilterContext *ctx = outlink->src;
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InterlaceContext *s = ctx->priv;
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while (ret >= 0 && !s->got_output)
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ret = ff_request_frame(ctx->inputs[0]);
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static const AVFilterPad inputs[] = {
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.type = AVMEDIA_TYPE_VIDEO,
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.filter_frame = filter_frame,
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static const AVFilterPad outputs[] = {
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.type = AVMEDIA_TYPE_VIDEO,
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.config_props = config_out_props,
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.request_frame = request_frame,
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AVFilter ff_vf_interlace = {
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.description = NULL_IF_CONFIG_SMALL("Convert progressive video into interlaced."),
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.priv_class = &class,
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.priv_size = sizeof(InterlaceContext),
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.query_formats = query_formats,