examples: add demuxing.c example

.gitignore

@@ -27,6 +27,7 @@
 /doc/avoptions_codec.texi
 /doc/avoptions_format.texi
 /doc/examples/decoding_encoding
+/doc/examples/demuxing
 /doc/examples/filtering_audio
 /doc/examples/filtering_video
 /doc/examples/metadata

doc/examples/Makefile

@@ -12,6 +12,7 @@ CFLAGS := $(shell pkg-config --cflags $(FFMPEG_LIBS)) $(CFLAGS)
 LDLIBS := $(shell pkg-config --libs $(FFMPEG_LIBS)) $(LDLIBS)
 
 EXAMPLES=       decoding_encoding                  \
+                demuxing                           \
                 filtering_video                    \
                 filtering_audio                    \
                 metadata                           \

doc/examples/demuxing.c

+/*
+ * Copyright (c) 2012 Stefano Sabatini
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * @file
+ * libavformat demuxing API use example.
+ *
+ * Show how to use the libavformat and libavcodec API to demux and
+ * decode video data.
+ */
+
+#include <libavutil/imgutils.h>
+#include <libavutil/timestamp.h>
+#include <libavformat/avformat.h>
+
+static AVFormatContext *fmt_ctx = NULL;
+static AVCodecContext *dec_ctx = NULL;
+static AVCodec *dec = NULL;
+static AVStream *stream = NULL;
+static const char *src_filename = NULL;
+static const char *dst_filename = NULL;
+static FILE *dst_file = NULL;
+static uint8_t *dst_data[4] = {NULL};
+static int dst_linesize[4];
+static int dst_bufsize;
+static int stream_idx;
+static AVFrame *frame = NULL;
+static AVPacket pkt;
+static int frame_count = 0;
+
+static int decode_packet(int *got_frame, int cached)
+{
+    int ret;
+
+    if (pkt.stream_index != stream_idx)
+        return 0;
+
+    /* decode video frame */
+    ret = avcodec_decode_video2(dec_ctx, frame, got_frame, &pkt);
+    if (ret < 0) {
+        fprintf(stderr, "Error decoding video frame\n");
+        return ret;
+    }
+
+    if (*got_frame) {
+        printf("frame%s n:%d coded_n:%d pts:%s\n",
+               cached ? "(cached)" : "",
+               frame_count++, frame->coded_picture_number,
+               av_ts2timestr(frame->pts, &dec_ctx->time_base));
+
+        /* copy decoded frame to destination buffer:
+         * this is required since rawvideo expect non aligned data */
+        av_image_copy(dst_data, dst_linesize,
+                      (const uint8_t **)(frame->data), frame->linesize,
+                      dec_ctx->pix_fmt, dec_ctx->width, dec_ctx->height);
+
+        /* write to rawvideo file */
+        fwrite(dst_data[0], 1, dst_bufsize, dst_file);
+    }
+
+    return ret;
+}
+
+int main (int argc, char **argv)
+{
+    int ret, got_frame;
+
+    if (argc != 3) {
+        fprintf(stderr, "usage: %s input_file output_file\n"
+                "API example program to show how to read frames from an input file.\n"
+                "This program reads frames from a file, decode them, and write them "
+                "to a rawvideo file named like output_file."
+                "\n", argv[0]);
+        exit(1);
+    }
+    src_filename = argv[1];
+    dst_filename = argv[2];
+
+    /* register all formats and codecs */
+    av_register_all();
+
+    /* open input file, and allocated format context */
+    if (avformat_open_input(&fmt_ctx, src_filename, NULL, NULL) < 0) {
+        fprintf(stderr, "Could not open source file %s\n", src_filename);
+        exit(1);
+    }
+
+    /* retrieve stream information */
+    if (avformat_find_stream_info(fmt_ctx, NULL) < 0) {
+        fprintf(stderr, "Could not find stream information\n");
+        exit(1);
+    }
+
+    ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
+    if (ret < 0) {
+        fprintf(stderr, "Could not find video stream in file\n");
+        goto end;
+    }
+    stream_idx = ret;
+    stream = fmt_ctx->streams[stream_idx];
+
+    /* find decoder for the stream */
+    dec_ctx = stream->codec;
+    dec = avcodec_find_decoder(dec_ctx->codec_id);
+    if (!dec) {
+        fprintf(stderr, "Failed to find any codec\n");
+        ret = 1;
+        goto end;
+    }
+
+    if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
+        fprintf(stderr, "Failed to open codec\n");
+        goto end;
+    }
+
+    /* dump input information to stderr */
+    av_dump_format(fmt_ctx, 0, src_filename, 0);
+
+    dst_file = fopen(dst_filename, "wb");
+    if (!dst_file) {
+        fprintf(stderr, "Could not open destination file %s\n", dst_filename);
+        ret = 1;
+        goto end;
+    }
+
+    frame = avcodec_alloc_frame();
+    if (!frame) {
+        fprintf(stderr, "Could not allocate video frame\n");
+        ret = 1;
+        goto end;
+    }
+
+    /* allocate image where the decoded image will be put */
+    ret = av_image_alloc(dst_data, dst_linesize,
+                         dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt, 1);
+    if (ret < 0) {
+        fprintf(stderr, "Could not alloc raw video buffer\n");
+        goto end;
+    }
+    dst_bufsize = ret;
+
+    /* initialize packet, set data to NULL, let the demuxer fill it */
+    av_init_packet(&pkt);
+    pkt.size = 0;
+    pkt.data = NULL;
+
+    printf("Demuxing file '%s' to '%s'\n", src_filename, dst_filename);
+
+    /* read frames from the file */
+    while (av_read_frame(fmt_ctx, &pkt) >= 0)
+        decode_packet(&got_frame, 0);
+
+    /* flush cached frames */
+    pkt.data = NULL;
+    pkt.size = 0;
+    do {
+        decode_packet(&got_frame, 1);
+    } while (got_frame);
+
+    printf("Demuxing succeeded. Play the output file with the command:\n"
+           "ffplay -f rawvideo -pix_fmt %s -video_size %dx%d %s\n",
+           av_get_pix_fmt_name(dec_ctx->pix_fmt), dec_ctx->width, dec_ctx->height,
+           dst_filename);
+
+end:
+    avcodec_close(dec_ctx);
+    avformat_close_input(&fmt_ctx);
+    if (dst_file)
+        fclose(dst_file);
+    av_free(frame);
+    av_free(dst_data[0]);
+
+    return ret < 0;
+}