Based on a patch by Andrew Kelley <[email protected]>
---
configure | 2 +
doc/Makefile | 3 +-
doc/examples/filter_audio.c | 362 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 366 insertions(+), 1 deletion(-)
create mode 100644 doc/examples/filter_audio.c
diff --git a/configure b/configure
index f4ee881..8d293d2 100755
--- a/configure
+++ b/configure
@@ -1094,6 +1094,7 @@ COMPONENT_LIST="
"
EXAMPLE_LIST="
+ filter_audio_example
output_example
transcode_aac_example
"
@@ -2017,6 +2018,7 @@ ocv_filter_deps="libopencv"
scale_filter_deps="swscale"
# examples
+filter_audio_example_deps="avfilter avutil"
output_example_deps="avcodec avformat avutil swscale"
transcode_aac_example_deps="avcodec avformat avresample"
diff --git a/doc/Makefile b/doc/Makefile
index e92e72f..cd7f23b 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -15,9 +15,10 @@ DOCS-$(CONFIG_POD2MAN) +=
$(MANPAGES) $(PODPAGES)
DOCS-$(CONFIG_TEXI2HTML) += $(HTMLPAGES)
DOCS = $(DOCS-yes)
+DOC_EXAMPLES-$(CONFIG_FILTER_AUDIO_EXAMPLE) += filter_audio
DOC_EXAMPLES-$(CONFIG_OUTPUT_EXAMPLE) += output
DOC_EXAMPLES-$(CONFIG_TRANSCODE_AAC_EXAMPLE) += transcode_aac
-ALL_DOC_EXAMPLES = output transcode_aac
+ALL_DOC_EXAMPLES = filter_audio output transcode_aac
DOC_EXAMPLES := $(DOC_EXAMPLES-yes:%=doc/examples/%$(EXESUF))
ALL_DOC_EXAMPLES := $(ALL_DOC_EXAMPLES:%=doc/examples/%$(EXESUF))
diff --git a/doc/examples/filter_audio.c b/doc/examples/filter_audio.c
new file mode 100644
index 0000000..58e780b
--- /dev/null
+++ b/doc/examples/filter_audio.c
@@ -0,0 +1,362 @@
+/*
+ * copyright (c) 2013 Andrew Kelley
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * libavfilter API use example.
+ *
+ * @example doc/examples/filter.c
+ * This example will generate a sine wave audio
+ * pass it through a simple filter chain, and then compute the md5 checksum of
+ * the output data
+ *
+ * The filter chain it uses is:
+ * (input) -> abuffer -> volume -> aformat -> abuffersink -> (output)
+ *
+ * abuffer: this provides the endpoint where you can feed the decoded samples.
+ * volume: in this example we hardcode it to 0.90
+ * aformat: this converts the samples to the samplefreq, channel layout,
+ * and sample format required by the audio device.
+ * abuffersink: this provides the endpoint where you can read the samples after
+ * they have passed through the filter chain.
+ */
+
+#include <inttypes.h>
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "libavutil/channel_layout.h"
+#include "libavutil/md5.h"
+#include "libavutil/opt.h"
+#include "libavutil/samplefmt.h"
+
+#include "libavfilter/avfilter.h"
+#include "libavfilter/buffersink.h"
+#include "libavfilter/buffersrc.h"
+
+#define INPUT_SAMPLERATE 48000
+#define INPUT_FORMAT AV_SAMPLE_FMT_FLTP
+#define INPUT_CHANNEL_LAYOUT AV_CH_LAYOUT_5POINT0
+
+#define VOLUME_VAL 0.90
+
+static int init_filter_graph(AVFilterGraph **graph, AVFilterContext **src,
AVFilterContext **sink)
+{
+ AVFilterGraph *filter_graph;
+ AVFilterContext *abuffer_ctx;
+ AVFilter *abuffer;
+ AVFilterContext *volume_ctx;
+ AVFilter *volume;
+ AVFilterContext *aformat_ctx;
+ AVFilter *aformat;
+ AVFilterContext *abuffersink_ctx;
+ AVFilter *abuffersink;
+
+ AVDictionary *options_dict = NULL;
+ uint8_t options_str[1024];
+ uint8_t ch_layout[64];
+
+ int err;
+
+ /* create a new filtergraph, which will contain all the filters */
+ filter_graph = avfilter_graph_alloc();
+ if (!filter_graph) {
+ fprintf(stderr, "Unable to create filter graph.\n");
+ return AVERROR(ENOMEM);
+ }
+
+ /* create the abuffer filter
+ * it will be used for feeding the data into the graph */
+ abuffer = avfilter_get_by_name("abuffer");
+ if (!abuffer) {
+ fprintf(stderr, "Could not find the abuffer filter.\n");
+ return AVERROR_FILTER_NOT_FOUND;
+ }
+
+ abuffer_ctx = avfilter_graph_alloc_filter(filter_graph, abuffer, "src");
+ if (!abuffer_ctx) {
+ fprintf(stderr, "Could not allocate the abuffer instance.\n");
+ return AVERROR(ENOMEM);
+ }
+
+ /* set the filter options through the AVOptions API */
+ av_get_channel_layout_string(ch_layout, sizeof(ch_layout), 0,
INPUT_CHANNEL_LAYOUT);
+ av_opt_set (abuffer_ctx, "channel_layout", ch_layout ,
AV_OPT_SEARCH_CHILDREN);
+ av_opt_set (abuffer_ctx, "sample_fmt",
av_get_sample_fmt_name(INPUT_FORMAT), AV_OPT_SEARCH_CHILDREN);
+ av_opt_set_q (abuffer_ctx, "time_base", (AVRational){ 1,
INPUT_SAMPLERATE }, AV_OPT_SEARCH_CHILDREN);
+ av_opt_set_int(abuffer_ctx, "sample_rate", INPUT_SAMPLERATE,
AV_OPT_SEARCH_CHILDREN);
+
+ /* now initialize the filter; we pass NULL options, since we have already
+ * set all the options above */
+ err = avfilter_init_str(abuffer_ctx, NULL);
+ if (err < 0) {
+ fprintf(stderr, "Could not initialize the abuffer filter.\n");
+ return err;
+ }
+
+ /* create volume filter */
+ volume = avfilter_get_by_name("volume");
+ if (!volume) {
+ fprintf(stderr, "Could not find the volume filter.\n");
+ return AVERROR_FILTER_NOT_FOUND;
+ }
+
+ volume_ctx = avfilter_graph_alloc_filter(filter_graph, volume, "volume");
+ if (!volume_ctx) {
+ fprintf(stderr, "Could not allocate the volume instance.\n");
+ return AVERROR(ENOMEM);
+ }
+
+ /* a different way of passing the options is as key/value pairs in a
+ * dictionary */
+ av_dict_set(&options_dict, "volume", AV_STRINGIFY(VOLUME_VAL), 0);
+ err = avfilter_init_dict(volume_ctx, &options_dict);
+ av_dict_free(&options_dict);
+ if (err < 0) {
+ fprintf(stderr, "Could not initialize the volume filter.\n");
+ return err;
+ }
+
+ /* create the aformat filter
+ * it ensures that the output is of the format we want */
+ aformat = avfilter_get_by_name("aformat");
+ if (!aformat) {
+ fprintf(stderr, "Could not find the aformat filter.\n");
+ return AVERROR_FILTER_NOT_FOUND;
+ }
+
+ aformat_ctx = avfilter_graph_alloc_filter(filter_graph, aformat,
"aformat");
+ if (!aformat_ctx) {
+ fprintf(stderr, "Could not allocate the aformat instance.\n");
+ return AVERROR(ENOMEM);
+ }
+
+ /* a third way of passing the options is in a string of the form
+ * key1=value1:key2=value2.... */
+ snprintf(options_str, sizeof(options_str),
+ "sample_fmts=%s:sample_rates=%d:channel_layouts=0x%"PRIx64,
+ av_get_sample_fmt_name(AV_SAMPLE_FMT_S16), 44100,
+ (uint64_t)AV_CH_LAYOUT_STEREO);
+ err = avfilter_init_str(aformat_ctx, options_str);
+ if (err < 0) {
+ av_log(NULL, AV_LOG_ERROR, "Could not initialize the aformat
filter.\n");
+ return err;
+ }
+
+ /* finally create the abuffersink filter
+ * it will be used to get the filtered data out of the graph */
+ abuffersink = avfilter_get_by_name("abuffersink");
+ if (!abuffersink) {
+ fprintf(stderr, "Could not find the abuffersink filter.\n");
+ return AVERROR_FILTER_NOT_FOUND;
+ }
+
+ abuffersink_ctx = avfilter_graph_alloc_filter(filter_graph, abuffersink,
"sink");
+ if (!abuffersink_ctx) {
+ fprintf(stderr, "Could not allocate the abuffersink instance.\n");
+ return AVERROR(ENOMEM);
+ }
+
+ /* this filter takes no options */
+ err = avfilter_init_str(abuffersink_ctx, NULL);
+ if (err < 0) {
+ fprintf(stderr, "Could not initialize the abuffersink instance.\n");
+ return err;
+ }
+
+ /* connect the filters
+ * in this simple case the filters just form a linear chain */
+ err = avfilter_link(abuffer_ctx, 0, volume_ctx, 0);
+ if (err >= 0)
+ err = avfilter_link(volume_ctx, 0, aformat_ctx, 0);
+ if (err >= 0)
+ err = avfilter_link(aformat_ctx, 0, abuffersink_ctx, 0);
+ if (err < 0) {
+ fprintf(stderr, "error connecting filters\n");
+ return err;
+ }
+
+ /* configure the graph*/
+ err = avfilter_graph_config(filter_graph, NULL);
+ if (err < 0) {
+ av_log(NULL, AV_LOG_ERROR, "error configuring the filter graph\n");
+ return err;
+ }
+
+ *graph = filter_graph;
+ *src = abuffer_ctx;
+ *sink = abuffersink_ctx;
+
+ return 0;
+}
+
+/* this function does something useful with the filtered data in this simple
+ * example we just print the md5 checksum of each plane to stdout */
+static int process_output(struct AVMD5 *md5, AVFrame *frame)
+{
+ int planar = av_sample_fmt_is_planar(frame->format);
+ int channels = av_get_channel_layout_nb_channels(frame->channel_layout);
+ int planes = planar ? channels : 1;
+ int bps = av_get_bytes_per_sample(frame->format);
+ int plane_size = bps * frame->nb_samples * (planar ? 1 : channels);
+ int i, j;
+
+ for (i = 0; i < planes; i++) {
+ uint8_t checksum[16];
+
+ av_md5_init(md5);
+ av_md5_sum(checksum, frame->extended_data[i], plane_size);
+
+ fprintf(stdout, "plane %d: 0x", i);
+ for (j = 0; j < sizeof(checksum); j++)
+ fprintf(stdout, "%02X", checksum[j]);
+ fprintf(stdout, "\n");
+ }
+ fprintf(stdout, "\n");
+
+ return 0;
+}
+
+/* this function constructs a frame of audio data to be filtered
+ * in this simple example we just synthesise sine wave */
+static int get_input(AVFrame *frame, int frame_num)
+{
+ int err, i, j;
+
+#define FRAME_SIZE 1024
+
+ /* setup the frame properties and allocate the buffer for the data */
+ frame->sample_rate = INPUT_SAMPLERATE;
+ frame->format = INPUT_FORMAT;
+ frame->channel_layout = INPUT_CHANNEL_LAYOUT;
+ frame->nb_samples = FRAME_SIZE;
+ frame->pts = frame_num * FRAME_SIZE;
+
+ err = av_frame_get_buffer(frame, 0);
+ if (err < 0)
+ return err;
+
+ /* fill the data for each channel */
+ for (i = 0; i < 5; i++) {
+ float *data = (float*)frame->extended_data[i];
+
+ for (j = 0; j < frame->nb_samples; j++)
+ data[j] = sin(2 * M_PI * (frame_num + j) * (i + 1) / FRAME_SIZE);
+ }
+
+ return 0;
+}
+
+int main(int argc, char *argv[])
+{
+ struct AVMD5 *md5;
+ AVFilterGraph *graph;
+ AVFilterContext *src, *sink;
+ AVFrame *frame;
+ uint8_t errstr[1024];
+ float duration;
+ int err, nb_frames, i;
+
+ if (argc < 2) {
+ fprintf(stderr, "Usage: %s <duration>\n", argv[0]);
+ return 1;
+ }
+
+ duration = atof(argv[1]);
+ nb_frames = duration * INPUT_SAMPLERATE / FRAME_SIZE;
+ if (nb_frames <= 0) {
+ fprintf(stderr, "Invalid duration: %s\n", argv[1]);
+ return 1;
+ }
+
+ avfilter_register_all();
+
+ /* allocate the frame we will be using to store the data */
+ frame = av_frame_alloc();
+ if (!frame) {
+ fprintf(stderr, "Error allocating the frame\n");
+ return 1;
+ }
+
+ md5 = av_md5_alloc();
+ if (!md5) {
+ fprintf(stderr, "Error allocating the MD5 context\n");
+ return 1;
+ }
+
+ /* setup the filtergraph */
+ err = init_filter_graph(&graph, &src, &sink);
+ if (err < 0) {
+ fprintf(stderr, "Unable to init filter graph:");
+ goto fail;
+ }
+
+ /* the main filtering loop */
+ for (i = 0; i < nb_frames; i++) {
+ /* get an input frame to be filtered */
+ err = get_input(frame, i);
+ if (err < 0) {
+ fprintf(stderr, "Error generating input frame:");
+ goto fail;
+ }
+
+ /* send the frame to the input of the filtergraph */
+ err = av_buffersrc_add_frame(src, frame);
+ if (err < 0) {
+ av_frame_unref(frame);
+ fprintf(stderr, "Error submitting the frame to the filtergraph:");
+ goto fail;
+ }
+
+ /* get all the filtered output that is available */
+ while ((err = av_buffersink_get_frame(sink, frame)) >= 0) {
+ /* now do something with our filtered frame */
+ err = process_output(md5, frame);
+ if (err < 0) {
+ fprintf(stderr, "Error processing the filtered frame:");
+ goto fail;
+ }
+ av_frame_unref(frame);
+ }
+
+ if (err == AVERROR(EAGAIN)) {
+ /* need to feed more frames in */
+ continue;
+ } else if (err == AVERROR_EOF) {
+ /* nothing more to do, finish */
+ break;
+ } else if (err < 0) {
+ /* an error occurred */
+ fprintf(stderr, "Error filtering the data:");
+ goto fail;
+ }
+ }
+
+ avfilter_graph_free(&graph);
+ av_frame_free(&frame);
+ av_freep(&md5);
+
+ return 0;
+fail:
+ av_strerror(err, errstr, sizeof(errstr));
+ fprintf(stderr, "%s\n", errstr);
+ return 1;
+}
--
1.7.10.4
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