diff options
author | Clément Bœsch <clement.boesch@smartjog.com> | 2011-10-24 19:11:10 +0400 |
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committer | Clément Bœsch <ubitux@gmail.com> | 2011-12-27 14:05:08 +0400 |
commit | 15a2a29ba3345083c95d8a920d8950267db8a6f5 (patch) | |
tree | 3362d52100a0ea4ef7b1a0edf0d88d122f68ca9b /libavfilter/vf_thumbnail.c | |
parent | b72544370aa22697cc28d4c85e642431fa591629 (diff) |
lavfi: add thumbnail video filter.
Diffstat (limited to 'libavfilter/vf_thumbnail.c')
-rw-r--r-- | libavfilter/vf_thumbnail.c | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c new file mode 100644 index 0000000000..b2f1e9483e --- /dev/null +++ b/libavfilter/vf_thumbnail.c @@ -0,0 +1,243 @@ +/* + * 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>. + * @url http://notbrainsurgery.livejournal.com/29773.html + */ + +#include "avfilter.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, void *opaque) +{ + 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(ENOMEM); + } + } + 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_INFO, "batch size: %d frames\n", thumb->n_frames); + return 0; +} + +static void 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]; + } +} + +/** + * @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 void 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; + + // no selection until the buffer of N frames is filled up + if (thumb->n < thumb->n_frames - 1) { + thumb->n++; + return; + } + + // 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)); + avfilter_start_frame(outlink, picref); + thumb->frames[best_frame_idx].buf = NULL; + avfilter_draw_slice(outlink, 0, inlink->h, 1); + avfilter_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 void null_start_frame(AVFilterLink *link, AVFilterBufferRef *picref) { } + +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) */ + while (thumb->n) { + int ret = avfilter_request_frame(link->src->inputs[0]); + if (ret < 0) + return ret; + } + return 0; +} + +static int poll_frame(AVFilterLink *link) +{ + ThumbContext *thumb = link->src->priv; + AVFilterLink *inlink = link->src->inputs[0]; + int ret, available_frames = avfilter_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 = avfilter_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 + }; + avfilter_set_common_pixel_formats(ctx, avfilter_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 = avfilter_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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