[FFmpeg-devel] [PATCH] examples: add demuxing example

Stefano Sabatini stefasab at gmail.com
Wed Aug 29 23:44:19 CEST 2012


---
 doc/examples/Makefile   |    3 +-
 doc/examples/demuxing.c |  199 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 201 insertions(+), 1 deletions(-)
 create mode 100644 doc/examples/demuxing.c

diff --git a/doc/examples/Makefile b/doc/examples/Makefile
index 287dfc4..dab12c1 100644
--- a/doc/examples/Makefile
+++ b/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                           \
@@ -29,7 +30,7 @@ muxing:            LDLIBS += -lm
 all: $(OBJS) $(EXAMPLES)
 
 clean-test:
-	$(RM) test*.pgm test.h264 test.mp2 test.sw test.mpg outscale*.pgm
+	$(RM) test*.pgm test.h264 test.mp2 test.sw test.mpg outscale*.pgm outdemux.raw
 
 clean: clean-test
 	$(RM) $(EXAMPLES) $(OBJS)
diff --git a/doc/examples/demuxing.c b/doc/examples/demuxing.c
new file mode 100644
index 0000000..621181f
--- /dev/null
+++ b/doc/examples/demuxing.c
@@ -0,0 +1,199 @@
+/*
+ * 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 for demuxing and
+ * decoding video data.
+ */
+
+#include <libavutil/imgutils.h>
+#include <libavutil/timestamp.h>
+#include <libavformat/avformat.h>
+
+
+int main (int argc, char **argv)
+{
+    AVFormatContext *fmtctx = NULL;
+    AVCodecContext *decctx = NULL;
+    AVCodec *dec = NULL;
+    AVStream *stream = NULL;
+    const char *src_filename = NULL, *dst_filename = "outdemux.raw";
+    FILE *dst_file = NULL;
+    uint8_t *dst_data[4] = {NULL};
+    int dst_linesize[4];
+    int dst_bufsize;
+    AVPacket pkt;
+    int stream_idx;
+    AVFrame *frame = NULL;
+    int got_frame, ret, frame_count = 0;
+
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s inputfile\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 outdemux.raw."
+                "\n", argv[0]);
+        exit(1);
+    }
+    src_filename = argv[1];
+
+    /* register all formats and codecs */
+    av_register_all();
+
+    /* open input file, and allocated format context */
+    if (avformat_open_input(&fmtctx, src_filename, NULL, NULL) < 0) {
+        fprintf(stderr, "Cannot open source file %s\n", src_filename);
+        exit(1);
+    }
+
+    /* retrieve stream information */
+    if (avformat_find_stream_info(fmtctx, NULL) < 0) {
+        fprintf(stderr, "Cannot find stream information\n");
+        exit(1);
+    }
+
+    ret = av_find_best_stream(fmtctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
+    if (ret < 0) {
+        fprintf(stderr, "Cannot find video stream in file\n");
+        goto end;
+    }
+    stream_idx = ret;
+    stream = fmtctx->streams[stream_idx];
+
+    /* find decoder for the stream */
+    decctx = stream->codec;
+    dec = avcodec_find_decoder(decctx->codec_id);
+    if (!dec) {
+        fprintf(stderr, "Failed to find any codec\n");
+        ret = 1;
+        goto end;
+    }
+
+    if ((ret = avcodec_open2(decctx, dec, NULL)) < 0) {
+        fprintf(stderr, "Failed to open codec\n");
+        goto end;
+    }
+
+    /* dump input information to stderr */
+    av_dump_format(fmtctx, 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,
+                         decctx->width, decctx->height, decctx->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(fmtctx, &pkt) >= 0) {
+        if (pkt.stream_index != stream_idx)
+            continue;
+
+        /* decode video frame */
+        ret = avcodec_decode_video2(decctx, frame, &got_frame, &pkt);
+        if (ret < 0) {
+            fprintf(stderr, "Error decoding video frame\n");
+            goto end;
+        }
+
+        if (got_frame) {
+            printf("frame n:%d coded_n:%d pts:%s\n",
+                   frame_count++, frame->coded_picture_number,
+                   av_ts2timestr(frame->pts, &decctx->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,
+                          decctx->pix_fmt, decctx->width, decctx->height);
+            /* write to rawvideo file */
+            fwrite(dst_data[0], 1, dst_bufsize, dst_file);
+        }
+    }
+
+    /* flush cached frames */
+    pkt.data = NULL;
+    pkt.size = 0;
+    do {
+        if (pkt.stream_index != stream_idx)
+            continue;
+
+        ret = avcodec_decode_video2(decctx, frame, &got_frame, &pkt);
+        if (ret < 0) {
+            fprintf(stderr, "Error decoding video frame\n");
+            goto end;
+        }
+
+        if (got_frame) {
+            printf("frame(cached) n:%d coded_n:%d pts:%s\n",
+                   frame_count++, frame->coded_picture_number,
+                   av_ts2timestr(frame->pts, &decctx->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,
+                          decctx->pix_fmt, decctx->width, decctx->height);
+            /* write to rawvideo file */
+            fwrite(dst_data[0], 1, dst_bufsize, dst_file);
+        }
+    } 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(decctx->pix_fmt), decctx->width, decctx->height,
+           dst_filename);
+
+end:
+    avcodec_close(decctx);
+    avformat_close_input(&fmtctx);
+    if (dst_file)
+        fclose(dst_file);
+    av_free(frame);
+    av_free(dst_data[0]);
+
+    return ret < 0;
+}
-- 
1.7.5.4



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