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-rw-r--r--libavfilter/vf_thumbnail.c246
1 files changed, 246 insertions, 0 deletions
diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c
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+/*
+ * Copyright (c) 2011 Smartjog S.A.S, Clément Bœsch <clement.boesch@smartjog.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Potential thumbnail lookup filter to reduce the risk of an inappropriate
+ * selection (such as a black frame) we could get with an absolute seek.
+ *
+ * Simplified version of algorithm by Vadim Zaliva <lord@crocodile.org>.
+ * @see http://notbrainsurgery.livejournal.com/29773.html
+ */
+
+#include "avfilter.h"
+#include "internal.h"
+
+#define HIST_SIZE (3*256)
+
+struct thumb_frame {
+ AVFilterBufferRef *buf; ///< cached frame
+ int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame
+};
+
+typedef struct {
+ int n; ///< current frame
+ int n_frames; ///< number of frames for analysis
+ struct thumb_frame *frames; ///< the n_frames frames
+} ThumbContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+ ThumbContext *thumb = ctx->priv;
+
+ if (!args) {
+ thumb->n_frames = 100;
+ } else {
+ int n = sscanf(args, "%d", &thumb->n_frames);
+ if (n != 1 || thumb->n_frames < 2) {
+ thumb->n_frames = 0;
+ av_log(ctx, AV_LOG_ERROR,
+ "Invalid number of frames specified (minimum is 2).\n");
+ return AVERROR(EINVAL);
+ }
+ }
+ thumb->frames = av_calloc(thumb->n_frames, sizeof(*thumb->frames));
+ if (!thumb->frames) {
+ av_log(ctx, AV_LOG_ERROR,
+ "Allocation failure, try to lower the number of frames\n");
+ return AVERROR(ENOMEM);
+ }
+ av_log(ctx, AV_LOG_VERBOSE, "batch size: %d frames\n", thumb->n_frames);
+ return 0;
+}
+
+static int draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
+{
+ int i, j;
+ AVFilterContext *ctx = inlink->dst;
+ ThumbContext *thumb = ctx->priv;
+ int *hist = thumb->frames[thumb->n].histogram;
+ AVFilterBufferRef *picref = inlink->cur_buf;
+ const uint8_t *p = picref->data[0] + y * picref->linesize[0];
+
+ // update current frame RGB histogram
+ for (j = 0; j < h; j++) {
+ for (i = 0; i < inlink->w; i++) {
+ hist[0*256 + p[i*3 ]]++;
+ hist[1*256 + p[i*3 + 1]]++;
+ hist[2*256 + p[i*3 + 2]]++;
+ }
+ p += picref->linesize[0];
+ }
+ return 0;
+}
+
+/**
+ * @brief Compute Sum-square deviation to estimate "closeness".
+ * @param hist color distribution histogram
+ * @param median average color distribution histogram
+ * @return sum of squared errors
+ */
+static double frame_sum_square_err(const int *hist, const double *median)
+{
+ int i;
+ double err, sum_sq_err = 0;
+
+ for (i = 0; i < HIST_SIZE; i++) {
+ err = median[i] - (double)hist[i];
+ sum_sq_err += err*err;
+ }
+ return sum_sq_err;
+}
+
+static int end_frame(AVFilterLink *inlink)
+{
+ int i, j, best_frame_idx = 0;
+ double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1;
+ AVFilterLink *outlink = inlink->dst->outputs[0];
+ ThumbContext *thumb = inlink->dst->priv;
+ AVFilterContext *ctx = inlink->dst;
+ AVFilterBufferRef *picref;
+
+ // keep a reference of each frame
+ thumb->frames[thumb->n].buf = inlink->cur_buf;
+ inlink->cur_buf = NULL;
+
+ // no selection until the buffer of N frames is filled up
+ if (thumb->n < thumb->n_frames - 1) {
+ thumb->n++;
+ return 0;
+ }
+
+ // average histogram of the N frames
+ for (j = 0; j < FF_ARRAY_ELEMS(avg_hist); j++) {
+ for (i = 0; i < thumb->n_frames; i++)
+ avg_hist[j] += (double)thumb->frames[i].histogram[j];
+ avg_hist[j] /= thumb->n_frames;
+ }
+
+ // find the frame closer to the average using the sum of squared errors
+ for (i = 0; i < thumb->n_frames; i++) {
+ sq_err = frame_sum_square_err(thumb->frames[i].histogram, avg_hist);
+ if (i == 0 || sq_err < min_sq_err)
+ best_frame_idx = i, min_sq_err = sq_err;
+ }
+
+ // free and reset everything (except the best frame buffer)
+ for (i = 0; i < thumb->n_frames; i++) {
+ memset(thumb->frames[i].histogram, 0, sizeof(thumb->frames[i].histogram));
+ if (i == best_frame_idx)
+ continue;
+ avfilter_unref_buffer(thumb->frames[i].buf);
+ thumb->frames[i].buf = NULL;
+ }
+ thumb->n = 0;
+
+ // raise the chosen one
+ picref = thumb->frames[best_frame_idx].buf;
+ av_log(ctx, AV_LOG_INFO, "frame id #%d (pts_time=%f) selected\n",
+ best_frame_idx, picref->pts * av_q2d(inlink->time_base));
+ ff_start_frame(outlink, picref);
+ thumb->frames[best_frame_idx].buf = NULL;
+ ff_draw_slice(outlink, 0, inlink->h, 1);
+ return ff_end_frame(outlink);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+ int i;
+ ThumbContext *thumb = ctx->priv;
+ for (i = 0; i < thumb->n_frames && thumb->frames[i].buf; i++) {
+ avfilter_unref_buffer(thumb->frames[i].buf);
+ thumb->frames[i].buf = NULL;
+ }
+ av_freep(&thumb->frames);
+}
+
+static int null_start_frame(AVFilterLink *link, AVFilterBufferRef *picref) { return 0; }
+
+static int request_frame(AVFilterLink *link)
+{
+ ThumbContext *thumb = link->src->priv;
+
+ /* loop until a frame thumbnail is available (when a frame is queued,
+ * thumb->n is reset to zero) */
+ do {
+ int ret = ff_request_frame(link->src->inputs[0]);
+ if (ret < 0)
+ return ret;
+ } while (thumb->n);
+ return 0;
+}
+
+static int poll_frame(AVFilterLink *link)
+{
+ ThumbContext *thumb = link->src->priv;
+ AVFilterLink *inlink = link->src->inputs[0];
+ int ret, available_frames = ff_poll_frame(inlink);
+
+ /* If the input link is not able to provide any frame, we can't do anything
+ * at the moment and thus have zero thumbnail available. */
+ if (!available_frames)
+ return 0;
+
+ /* Since at least one frame is available and the next frame will allow us
+ * to compute a thumbnail, we can return 1 frame. */
+ if (thumb->n == thumb->n_frames - 1)
+ return 1;
+
+ /* we have some frame(s) available in the input link, but not yet enough to
+ * output a thumbnail, so we request more */
+ ret = ff_request_frame(inlink);
+ return ret < 0 ? ret : 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+ static const enum PixelFormat pix_fmts[] = {
+ PIX_FMT_RGB24, PIX_FMT_BGR24,
+ PIX_FMT_NONE
+ };
+ ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
+ return 0;
+}
+
+AVFilter avfilter_vf_thumbnail = {
+ .name = "thumbnail",
+ .description = NULL_IF_CONFIG_SMALL("Select the most representative frame in a given sequence of consecutive frames."),
+ .priv_size = sizeof(ThumbContext),
+ .init = init,
+ .uninit = uninit,
+ .query_formats = query_formats,
+ .inputs = (const AVFilterPad[]) {
+ { .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .get_video_buffer = ff_null_get_video_buffer,
+ .start_frame = null_start_frame,
+ .draw_slice = draw_slice,
+ .end_frame = end_frame,
+ },{ .name = NULL }
+ },
+ .outputs = (const AVFilterPad[]) {
+ { .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .request_frame = request_frame,
+ .poll_frame = poll_frame,
+ .rej_perms = AV_PERM_REUSE2,
+ },{ .name = NULL }
+ },
+};
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