add mediathumb utility

Makefile

@@ -1,33 +1,41 @@
 RM      := rm -f
 CFLAGS  := -O3 -Wall -Isrc -I/usr/include/ffmpeg
-LIBS    := -lavformat -lavutil -lavcodec
+LIBS    := -lavformat -lavutil -lavcodec -lswscale
 LDFLAGS :=
 INSTALL ?= install
 PREFIX  ?= /usr/local
 
-COMMON_OBJECTS     := build/validation.o
+COMMON_OBJECTS     := build/validation.o build/png.o
 MEDIASTAT_OBJECTS  := build/stat.o
+MEDIATHUMB_OBJECTS := build/thumb.o
 
 # Phony rules
 .PHONY: all mediastat clean
 
-all: mediastat 
+all: mediastat mediathumb
 
 install: all
 	$(INSTALL) build/mediastat $(PREFIX)/bin/mediastat
+	$(INSTALL) build/mediathumb $(PREFIX)/bin/mediathumb
 
 uninstall:
 	$(RM) -rf $(PREFIX)/bin/mediastat
+	$(RM) -rf $(PREFIX)/bin/mediathumb
 
 mediastat: build/mediastat
 
+mediathumb: build/mediathumb
+
 clean:
-	$(RM) $(COMMON_OBJECTS) $(MEDIASTAT_OBJECTS)
+	$(RM) $(COMMON_OBJECTS) $(MEDIASTAT_OBJECTS)$(MEDIATHUMB_OBJECTS)
 
 # Build rules
 build/mediastat: $(COMMON_OBJECTS) $(MEDIASTAT_OBJECTS)
 	$(CC) $^ $(LDFLAGS) $(LIBS) -o $@
 
+build/mediathumb: $(COMMON_OBJECTS) $(MEDIATHUMB_OBJECTS)
+	$(CC) $^ $(LDFLAGS) $(LIBS) -o $@
+
 build/%.o: src/%.c
 	$(CC) $(CFLAGS) -MMD -c $< -o $@
 

src/png.c

@@ -0,0 +1,106 @@
+#include <libavformat/avformat.h>
+#include <libswscale/swscale.h>
+#include "png.h"
+
+int mediatools_write_frame_to_png(AVFrame *in_frame, const char *path)
+{
+    struct SwsContext *sws_ctx = NULL;
+    AVFormatContext *format = NULL;
+    AVOutputFormat *png = NULL;
+    AVCodecContext *vctx = NULL;
+    AVStream *vstream = NULL;
+    AVFrame *out_frame = NULL;
+    AVCodec *vcodec = NULL;
+    AVPacket pkt = { 0 };
+
+    int ret = -1;
+
+    png = av_guess_format(NULL, NULL, "image/png");
+    vcodec = avcodec_find_encoder(AV_CODEC_ID_APNG);
+    vctx = avcodec_alloc_context3(vcodec);
+    format = avformat_alloc_context();
+    out_frame = av_frame_alloc();
+
+    if (!format || !vctx || !vcodec || !png || !out_frame)
+        goto error;
+
+    format->oformat = png;
+    format->url = av_strdup(path);
+
+    vstream = avformat_new_stream(format, NULL);
+    if (!vstream)
+        goto error;
+
+    if (png->flags & AVFMT_GLOBALHEADER)
+        vctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
+
+    vctx->time_base = (AVRational) { 1, 1 };
+    vctx->width = in_frame->width;
+    vctx->height = in_frame->height;
+    vctx->pix_fmt = AV_PIX_FMT_RGBA;
+
+    if (avcodec_parameters_from_context(vstream->codecpar, vctx) < 0)
+        goto error;
+
+    if (avcodec_open2(vctx, vcodec, NULL) < 0)
+        goto error;
+
+    avio_open(&format->pb, path, AVIO_FLAG_WRITE);
+
+    if (avformat_write_header(format, NULL) < 0)
+        goto error;
+
+    av_init_packet(&pkt);
+
+    out_frame->format = AV_PIX_FMT_RGBA;
+    out_frame->width = in_frame->width;
+    out_frame->height = in_frame->height;
+
+    if (av_frame_get_buffer(out_frame, 0) < 0)
+        goto error;
+
+    if (av_frame_make_writable(out_frame) < 0)
+        goto error;
+
+    // Rewrite frame into correct color format
+
+    sws_ctx = sws_getContext(in_frame->width, in_frame->height, in_frame->format, out_frame->width, out_frame->height, AV_PIX_FMT_RGBA, SWS_LANCZOS, NULL, NULL, NULL);
+    if (!sws_ctx)
+        goto error;
+
+    sws_scale(sws_ctx, (const uint8_t **)in_frame->data, in_frame->linesize, 0, in_frame->height, out_frame->data, out_frame->linesize);
+    if (avcodec_send_frame(vctx, out_frame) < 0)
+        goto error;
+    if (avcodec_send_frame(vctx, NULL) < 0)
+        goto error;
+    if (avcodec_receive_packet(vctx, &pkt) < 0)
+        goto error;
+
+    pkt.stream_index = vstream->index;
+    pkt.pts = 1;
+    pkt.dts = 1;
+
+    if (av_write_frame(format, &pkt) < 0)
+        goto error;
+
+    av_packet_unref(&pkt);
+
+    if (av_write_trailer(format) < 0)
+        goto error;
+
+    ret = 0;
+
+error:
+    if (sws_ctx)
+        sws_freeContext(sws_ctx);
+    if (format->pb)
+        avio_close(format->pb);
+    if (vctx)
+        avcodec_free_context(&vctx);
+    if (out_frame)
+        av_frame_free(&out_frame);
+    if (format)
+        avformat_free_context(format);
+
+    return ret;
+}

src/png.h

@@ -0,0 +1,8 @@
+#ifndef _PNG_H_DEFINED
+#define _PNG_H_DEFINED
+
+#include <libavformat/avformat.h>
+
+int mediatools_write_frame_to_png(AVFrame *in_frame, const char *path);
+
+#endif

src/stat.c

@@ -7,6 +7,15 @@
 
 #include "validation.h"
 
+static int64_t start_time(AVStream *stream)
+{
+    if (stream->start_time == AV_NOPTS_VALUE) {
+        return 0;
+    }
+
+    return stream->start_time;
+}
+
 int main(int argc, char *argv[])
 {
     AVFormatContext *format = NULL;
@@ -67,8 +76,8 @@ int main(int argc, char *argv[])
         av_packet_unref(&pkt);
     }
 
-    AVRational tb  = format->streams[last_stream]->time_base;
+    AVStream *stream = format->streams[last_stream];
-    AVRational dur = av_mul_q(av_make_q(last_pts, 1), tb);
+    AVRational dur   = av_mul_q(av_make_q(last_pts - start_time(stream), 1), stream->time_base);
 
     if (!mediatools_validate_duration(dur))
         return -1;

src/thumb.c

@@ -0,0 +1,111 @@
+#include <libavformat/avformat.h>
+#include <stdio.h>
+#include "png.h"
+
+int main(int argc, char *argv[])
+{
+    AVFormatContext *format = NULL;
+    AVCodecContext *vctx = NULL;
+    AVStream *vstream = NULL;
+    AVCodec *vcodec = NULL;
+    AVFrame *frame = NULL;
+    AVPacket pkt;
+
+    int found = 0;
+
+    if (argc != 4) {
+        printf("Expected an input, a time, and an output\n");
+        return -1;
+    }
+
+    av_log_set_level(AV_LOG_QUIET);
+
+    const char *input = argv[1];
+    const char *output = argv[3];
+    AVRational time = av_d2q(atof(argv[2]), INT_MAX);
+
+    if (avformat_open_input(&format, input, NULL, NULL) != 0) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    if (avformat_find_stream_info(format, NULL) < 0) {
+        printf("Couldn't read file \n");
+        return -1;
+    }
+
+    int vstream_idx = av_find_best_stream(format, AVMEDIA_TYPE_VIDEO, -1, -1, &vcodec, 0);
+    if (vstream_idx < 0) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    vstream = format->streams[vstream_idx];
+
+    // Set up decoding context
+    vctx = avcodec_alloc_context3(vcodec);
+    if (!vctx) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    if (avcodec_parameters_to_context(vctx, vstream->codecpar) < 0) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    if (avcodec_open2(vctx, vcodec, NULL) < 0) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    frame = av_frame_alloc();
+    if (!frame) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    av_seek_frame(format, -1, 0, AVSEEK_FLAG_BACKWARD);
+
+    // Loop until we get to the first video frame past the intended pts,
+    // decoding all video frames along the way.
+
+    while (!found && av_read_frame(format, &pkt) >= 0) {
+        if (pkt.stream_index == vstream_idx) {
+            AVRational cur_time  = { pkt.pts, vstream->time_base.den };
+            AVRational next_time = { pkt.pts + pkt.duration, vstream->time_base.den };
+
+            if (avcodec_send_packet(vctx, &pkt) != 0 || avcodec_receive_frame(vctx, frame) != 0) {
+                // Decoder returned an error
+                printf("Couldn't read file\n");
+                return -1;
+            }
+
+            // If this is the first frame past the requested time or the
+            // current frame contains the requested time, pick this frame.
+
+            if (av_cmp_q(cur_time, time) >= 0 || (av_cmp_q(cur_time, time) <= 0 && av_cmp_q(next_time, time) >= 0)) {
+                found = 1;
+
+                // Found the frame; write to the provided file
+                if (mediatools_write_frame_to_png(frame, output) < 0) {
+                    printf("Couldn't read file\n");
+                    return -1;
+                }
+            }
+        }
+
+        av_packet_unref(&pkt);
+    }
+
+    if (!found) {
+        printf("Couldn't read file\n");
+        return -1;
+    }
+
+    av_frame_free(&frame);
+    avcodec_free_context(&vctx);
+    avformat_close_input(&format);
+
+    return 0;
+}