Add very simple abstraction [video_decode.c] of libav

..and an example program using it: frame_to_pgm.

4 files changed, 219 insertions, 2 deletions

diff --git a/src/Makefile b/src/Makefile
index 29ffd29..fbdb424 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,11 +1,14 @@
-CFLAGS=-std=c99 -Wall
+CFLAGS=-std=c99 -Wall -Wstrict-prototypes -Wmissing-prototypes -Wno-unused-parameter
 LibAV=`pkg-config --cflags --libs libavcodec`
 LIBAV_DECODE_FLAGS=$(shell pkg-config --libs --cflags libavformat libavcodec libavutil libswscale)
 
-all: advtime decode_frame
+all: advtime decode_frame frame_to_pgm
 
 advtime: advtime.c
 	gcc ${LibAV} advtime.c -o $@
 
 decode_frame: decode_frame.c
 	gcc $(CFLAGS) $(LIBAV_DECODE_FLAGS) decode_frame.c -o $@
+
+frame_to_pgm: frame_to_pgm.c video_decode.c
+	gcc $(CFLAGS) $(LIBAV_DECODE_FLAGS) frame_to_pgm.c video_decode.c -o $@
diff --git a/src/frame_to_pgm.c b/src/frame_to_pgm.c
new file mode 100644
index 0000000..f018099
--- /dev/null
+++ b/src/frame_to_pgm.c
@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "video_decode.h"
+
+static void
+pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
+{
+    FILE *f;
+    int i;
+
+    f = fopen(filename, "w");
+    fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
+    for(i=0; i < ysize; i++)
+        fwrite(buf + i * wrap, 1, xsize, f);
+    fclose(f);
+}
+
+int
+main(int argc, char **argv)
+{
+	struct video_decode *vd;
+	struct video_frame *frame;
+	int ret;
+	int64_t timestamp = 0;
+
+	if (argc < 3)
+		return 1;
+
+	if (argc == 4 && strtol(argv[3], NULL, 10) > 0)
+		timestamp = strtol(argv[3], NULL, 10);
+
+	ret = video_decode_init(&vd, argv[1], timestamp);
+	if (ret < 0)
+		return -ret;
+		
+	ret = video_decode_get_frame(vd, &frame);
+	if (ret < 0)
+		return -ret;
+
+	pgm_save(frame->data, frame->stride, frame->width, frame->height,
+		 argv[2]);
+}
diff --git a/src/video_decode.c b/src/video_decode.c
new file mode 100644
index 0000000..87d3483
--- /dev/null
+++ b/src/video_decode.c
@@ -0,0 +1,151 @@
+#define DEBUG 1
+#include "video_decode.h"
+
+#include <libavutil/avutil.h>
+#include <libavformat/avformat.h>
+#include <libavcodec/avcodec.h>
+#include <libswscale/swscale.h>
+
+
+struct video_decode {
+	AVFormatContext *fmt_ctx;
+	AVCodecContext *codec_ctx;
+	AVCodec *codec;
+	int stream;
+};
+
+struct video_frame_priv {
+	struct video_frame base;
+	AVFrame *frame;
+};
+
+int
+video_decode_init(struct video_decode **vd_out, char *file, int64_t ts)
+{
+	struct video_decode *vd;
+
+	vd = calloc(1, sizeof *vd);
+	if (vd == NULL)
+		return -1;
+
+	av_register_all();
+
+	vd->fmt_ctx = NULL;
+	vd->codec_ctx = NULL;
+
+	if (avformat_open_input(&vd->fmt_ctx, file, NULL, NULL) != 0)
+		return -1;
+
+	if (avformat_find_stream_info(vd->fmt_ctx, NULL) < 0)
+		return -2;
+#if DEBUG
+	av_dump_format(vd->fmt_ctx, 0, file, 0);
+#endif
+	vd->stream = av_find_best_stream(vd->fmt_ctx, AVMEDIA_TYPE_VIDEO,
+					     -1, -1, NULL, 0);
+	if (vd->stream == -1)
+		return -3;
+
+	vd->codec_ctx = vd->fmt_ctx->streams[vd->stream]->codec;
+
+	if (vd->fmt_ctx->start_time != AV_NOPTS_VALUE)
+		ts += vd->fmt_ctx->start_time;
+	/* FIXME: Check size */
+	avformat_seek_file(vd->fmt_ctx, vd->stream, INT64_MIN, ts, INT64_MAX,0);
+
+	vd->codec = avcodec_find_decoder(vd->codec_ctx->codec_id);
+	if (vd->codec == NULL) {
+		fprintf(stderr, "Failed to find decoder!\n");
+		return -4;
+	}
+#if DEBUG
+	printf("has cap truncated: %d\n",
+	       vd->codec->capabilities & CODEC_CAP_TRUNCATED);
+#endif
+#if 0
+	if (codec->capabilities & CODEC_CAP_TRUNCATED)
+		codec_ctx->flags |= CODEC_FLAG_TRUNCATED;
+#endif
+	if (avcodec_open2(vd->codec_ctx, vd->codec, NULL) < 0) {
+		fprintf(stderr, "Failed to open codec!\n");
+		return -5;
+	}
+
+	*vd_out = vd;
+	return 0;
+}
+
+void
+video_decode_uninit(struct video_decode **_vd)
+{
+	struct video_decode *vd = *_vd;
+
+	*_vd = NULL;
+	avcodec_close(vd->codec_ctx);
+	avformat_close_input(&vd->fmt_ctx);
+	free(vd);
+}
+
+int
+video_decode_get_frame(struct video_decode *vd, struct video_frame **frame)
+{
+	struct video_frame_priv *f;
+	AVPacket packet;
+	int decoded, got_picture;
+
+	f = calloc(1, sizeof *f);
+	if (f == NULL)
+		return -1;
+
+	packet.data = NULL;
+	do {
+		if (packet.data != NULL)
+			av_free_packet(&packet);
+		if (av_read_frame(vd->fmt_ctx, &packet) < 0) {
+			fprintf(stderr, "Found no video stream packet!\n");
+			return -1;
+		}
+	} while (packet.stream_index != vd->stream);
+
+	f->frame = avcodec_alloc_frame();
+
+	do {
+#if DEBUG
+		printf("packet.data: %p, packet.siz: %d, packet.strm_idx: %d\n",
+		       packet.data, packet.size, packet.stream_index);
+#endif
+		decoded = avcodec_decode_video2(vd->codec_ctx, f->frame,
+						&got_picture, &packet);
+		if (decoded < 0) {
+			fprintf(stderr, "Error while decoding frame!\n");
+			return -2;
+		}
+#if DEBUG
+		printf("bytes_decoded: %d, got_picture: %d\n",
+		       decoded, got_picture);
+#endif
+		
+	} while (got_picture == 0 && packet.size > 0);
+	av_free_packet(&packet);
+	if (got_picture == 0)
+		return -3;
+
+	f->base.data = f->frame->data[0];
+	f->base.width = vd->codec_ctx->width;
+	f->base.height = vd->codec_ctx->height;
+	f->base.stride = f->frame->linesize[0];
+
+	*frame = &f->base;
+
+	return 0;
+}
+
+void
+video_decode_free_frame(struct video_frame **frame)
+{
+	struct video_frame_priv *f = (struct video_frame_priv *) *frame;
+
+	*frame = NULL;
+	av_free(f->frame);
+	free(f);
+}
diff --git a/src/video_decode.h b/src/video_decode.h
new file mode 100644
index 0000000..64127f3
--- /dev/null
+++ b/src/video_decode.h
@@ -0,0 +1,19 @@
+#include <stdint.h>
+
+struct video_decode;
+struct video_frame {
+	uint8_t *data;
+	int width, height, stride;
+};
+
+int
+video_decode_init(struct video_decode **vd, char *file, int64_t timestamp);
+
+void
+video_decode_uninit(struct video_decode **vd);
+
+int
+video_decode_get_frame(struct video_decode *vd, struct video_frame **frame);
+
+void
+video_decode_free_frame(struct video_frame **frame);