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Diffstat (limited to 'libavfilter/vf_thumbnail.c')
-rw-r--r-- | libavfilter/vf_thumbnail.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c new file mode 100644 index 0000000..1883154 --- /dev/null +++ b/libavfilter/vf_thumbnail.c @@ -0,0 +1,239 @@ +/* + * 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 "libavutil/opt.h" +#include "avfilter.h" +#include "internal.h" + +#define HIST_SIZE (3*256) + +struct thumb_frame { + AVFrame *buf; ///< cached frame + int histogram[HIST_SIZE]; ///< RGB color distribution histogram of the frame +}; + +typedef struct { + const AVClass *class; + int n; ///< current frame + int n_frames; ///< number of frames for analysis + struct thumb_frame *frames; ///< the n_frames frames + AVRational tb; ///< copy of the input timebase to ease access +} ThumbContext; + +#define OFFSET(x) offsetof(ThumbContext, x) +#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM + +static const AVOption thumbnail_options[] = { + { "n", "set the frames batch size", OFFSET(n_frames), AV_OPT_TYPE_INT, {.i64=100}, 2, INT_MAX, FLAGS }, + { NULL } +}; + +AVFILTER_DEFINE_CLASS(thumbnail); + +static av_cold int init(AVFilterContext *ctx) +{ + ThumbContext *thumb = ctx->priv; + + 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; +} + +/** + * @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 AVFrame *get_best_frame(AVFilterContext *ctx) +{ + AVFrame *picref; + ThumbContext *thumb = ctx->priv; + int i, j, best_frame_idx = 0; + int nb_frames = thumb->n; + double avg_hist[HIST_SIZE] = {0}, sq_err, min_sq_err = -1; + + // average histogram of the N frames + for (j = 0; j < FF_ARRAY_ELEMS(avg_hist); j++) { + for (i = 0; i < nb_frames; i++) + avg_hist[j] += (double)thumb->frames[i].histogram[j]; + avg_hist[j] /= nb_frames; + } + + // find the frame closer to the average using the sum of squared errors + for (i = 0; i < nb_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 < nb_frames; i++) { + memset(thumb->frames[i].histogram, 0, sizeof(thumb->frames[i].histogram)); + if (i != best_frame_idx) + av_frame_free(&thumb->frames[i].buf); + } + 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 " + "from a set of %d images\n", best_frame_idx, + picref->pts * av_q2d(thumb->tb), nb_frames); + thumb->frames[best_frame_idx].buf = NULL; + + return picref; +} + +static int filter_frame(AVFilterLink *inlink, AVFrame *frame) +{ + int i, j; + AVFilterContext *ctx = inlink->dst; + ThumbContext *thumb = ctx->priv; + AVFilterLink *outlink = ctx->outputs[0]; + int *hist = thumb->frames[thumb->n].histogram; + const uint8_t *p = frame->data[0]; + + // keep a reference of each frame + thumb->frames[thumb->n].buf = frame; + + // update current frame RGB histogram + for (j = 0; j < inlink->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 += frame->linesize[0]; + } + + // no selection until the buffer of N frames is filled up + thumb->n++; + if (thumb->n < thumb->n_frames) + return 0; + + return ff_filter_frame(outlink, get_best_frame(ctx)); +} + +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++) + av_frame_free(&thumb->frames[i].buf); + av_freep(&thumb->frames); +} + +static int request_frame(AVFilterLink *link) +{ + AVFilterContext *ctx = link->src; + ThumbContext *thumb = ctx->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(ctx->inputs[0]); + if (ret == AVERROR_EOF && thumb->n) { + ret = ff_filter_frame(link, get_best_frame(ctx)); + if (ret < 0) + return ret; + ret = AVERROR_EOF; + } + if (ret < 0) + return ret; + } while (thumb->n); + return 0; +} + +static int config_props(AVFilterLink *inlink) +{ + AVFilterContext *ctx = inlink->dst; + ThumbContext *thumb = ctx->priv; + + thumb->tb = inlink->time_base; + return 0; +} + +static int query_formats(AVFilterContext *ctx) +{ + static const enum AVPixelFormat pix_fmts[] = { + AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24, + AV_PIX_FMT_NONE + }; + ff_set_common_formats(ctx, ff_make_format_list(pix_fmts)); + return 0; +} + +static const AVFilterPad thumbnail_inputs[] = { + { + .name = "default", + .type = AVMEDIA_TYPE_VIDEO, + .config_props = config_props, + .filter_frame = filter_frame, + }, + { NULL } +}; + +static const AVFilterPad thumbnail_outputs[] = { + { + .name = "default", + .type = AVMEDIA_TYPE_VIDEO, + .request_frame = request_frame, + }, + { NULL } +}; + +AVFilter ff_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 = thumbnail_inputs, + .outputs = thumbnail_outputs, + .priv_class = &thumbnail_class, +}; |