This is my code which copy from doc/examples/filter_audio.c
---------------------------------------
//===============================================filter===========
//audio : abuffer -> volume -> aformat -> abuffersink
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) {
loge("Unable to create filter graph.");
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) {
loge("Could not find the abuffer filter.");
return AVERROR_FILTER_NOT_FOUND;
}else{
logd("find abuffer filter.");
}
abuffer_ctx = avfilter_graph_alloc_filter(filter_graph, abuffer, "src");
if (!abuffer_ctx) {
loge("Could not allocate the abuffer instance.");
return AVERROR(ENOMEM);
}
/* Set the filter options through the AVOptions API. */
av_get_channel_layout_string(ch_layout, sizeof(ch_layout), 0,
AV_CH_LAYOUT_MONO); //TODO
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(AV_SAMPLE_FMT_S16), AV_OPT_SEARCH_CHILDREN);//TODO
av_opt_set_q (abuffer_ctx, "time_base", (AVRational){ 1, 16000 },
AV_OPT_SEARCH_CHILDREN);//TODO
av_opt_set_int(abuffer_ctx, "sample_rate", 16000,
AV_OPT_SEARCH_CHILDREN);//TODO
/* 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) {
loge("Could not initialize the abuffer filter.");
return err;
}
/* Create volume filter. */
volume = avfilter_get_by_name("volume");
if (!volume) {
loge("Could not find the volume filter.");
return AVERROR_FILTER_NOT_FOUND;
}else{
logd("find volume filter.");
}
volume_ctx = avfilter_graph_alloc_filter(filter_graph, volume, "volume");
if (!volume_ctx) {
loge("Could not allocate the volume instance.");
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(1.5), 0);//150% of
current volume
av_dict_set(&options_dict, "volume", AV_STRINGIFY(0.90), 0);
err = avfilter_init_dict(volume_ctx, &options_dict);
av_dict_free(&options_dict);
if (err < 0) {
loge("Could not initialize the volume filter.");
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) {
loge("Could not find the aformat filter.");
return AVERROR_FILTER_NOT_FOUND;
}else{
logd("find aformat filter.");
}
aformat_ctx = avfilter_graph_alloc_filter(filter_graph, aformat, "aformat");
if (!aformat_ctx) {
loge("Could not allocate the aformat instance.");
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), 16000,
(uint64_t)AV_CH_LAYOUT_MONO);
err = avfilter_init_str(aformat_ctx, options_str);
if (err < 0) {
//av_log(NULL, AV_LOG_ERROR, "Could not initialize the aformat
filter.\n");
loge("Could not initialize the aformat filter.");
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) {
loge("Could not find the abuffersink filter.");
return AVERROR_FILTER_NOT_FOUND;
}else{
logd("find abuffersink filter.");
}
abuffersink_ctx = avfilter_graph_alloc_filter(filter_graph, abuffersink,
"sink");
if (!abuffersink_ctx) {
loge("Could not allocate the abuffersink instance.");
return AVERROR(ENOMEM);
}
/* This filter takes no options. */
err = avfilter_init_str(abuffersink_ctx, NULL);
if (err < 0) {
loge("Could not initialize the abuffersink instance.");
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)//zero on success
err = avfilter_link(volume_ctx, 0, aformat_ctx, 0);
if (err >= 0)
err = avfilter_link(aformat_ctx, 0, abuffersink_ctx, 0);
if (err < 0) {
loge("Error connecting filters");
return err;
}
/* Configure the graph. */
err = avfilter_graph_config(filter_graph, NULL);
if (err < 0) {
uint8_t errstr[1024];
av_strerror(err, errstr, sizeof(errstr));
//av_log(NULL, AV_LOG_ERROR, "Error configuring the filter graph\n");
loge("Error configuring the filter graph:%d,%s", err, errstr);
return err;
}
*graph = filter_graph;
*src = abuffer_ctx;
*sink = abuffersink_ctx;
return 0;
}
--------------------------------------
the output log is:
:find abuffer filter.
: find volume filter.
: find aformat filter.
: find abuffersink filter.
: Error configuring the filter graph:-22,Invalid argument
can any friends help me?thanks so much for your help.
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