最后，我通过这是为我的设置创建滤波器的代码(重采样为44.1KHz)

This is the code of the filter creation for my setup (resampling to 44.1KHz)

AVFilterGraph *filter_graph = NULL;
AVFilterContext *buffersrc_ctx = NULL;
AVFilterContext *buffersink_ctx = NULL;
QString filter_description = "aresample=44100,aformat=sample_fmts=fltp:channel_layouts=stereo,asetnsamples=n=1024:p=0";
/**
* Initialize conversion filter */
int initialize_audio_filter(AVStream *inputStream) {
char args[512];
int ret;
AVFilter *buffersrc = avfilter_get_by_name("abuffer");
AVFilter *buffersink = avfilter_get_by_name("abuffersink");
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
filter_graph = avfilter_graph_alloc();
const enum AVSampleFormat out_sample_fmts[] = {AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_NONE};
const int64_t out_channel_layouts[] = {AV_CH_LAYOUT_STEREO, -1};
const int out_sample_rates[] = {44100, -1};

snprintf(args, sizeof(args), "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%" PRIx64,
         inputStream->codec->time_base.num, inputStream->codec->time_base.den,
         inputStream->codec->sample_rate,
         av_get_sample_fmt_name(inputStream->codec->sample_fmt),
         inputStream->codec->channel_layout);
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph);

if (ret < 0) {
    svsCritical("", QString("Could not create filter graph, error: %1").arg(svsAvErrorToFormattedString(ret)))
    return -1;
}

ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph);

if (ret < 0) {
    svsCritical("", QString("Cannot create buffer sink, error: %1").arg(svsAvErrorToFormattedString(ret)))
    return ret;
}

ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
                          AV_OPT_SEARCH_CHILDREN);

if (ret < 0) {
    svsCritical("", QString("Cannot set output sample format, error: %1").arg(svsAvErrorToFormattedString(ret)))
    return ret;
}

ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
                          AV_OPT_SEARCH_CHILDREN);

if (ret < 0) {
    svsCritical("", QString("Cannot set output channel layout, error: %1").arg(svsAvErrorToFormattedString(ret)))
    return ret;
}

ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
                          AV_OPT_SEARCH_CHILDREN);

if (ret < 0) {
    svsCritical("", QString("Cannot set output sample rate, error: %1").arg(svsAvErrorToFormattedString(ret)))
    return ret;
}

/* Endpoints for the filter graph. */
outputs -> name = av_strdup("in");
outputs -> filter_ctx = buffersrc_ctx;
outputs -> pad_idx = 0;
outputs -> next = NULL;
/* Endpoints for the filter graph. */
inputs -> name = av_strdup("out");
inputs -> filter_ctx = buffersink_ctx;
inputs -> pad_idx = 0;
inputs -> next = NULL;

if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_description.toStdString().c_str(), &inputs, &outputs, NULL)) < 0) {
    svsCritical("", QString("Could not add the filter to graph, error: %1").arg(svsAvErrorToFormattedString(ret)))
}

if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0) {
    svsCritical("", QString("Could not configure the graph, error: %1").arg(svsAvErrorToFormattedString(ret)))
}

/* Print summary of the sink buffer
 * Note: args buffer is reused to store channel layout string */
AVFilterLink *outlink = buffersink_ctx->inputs[0];
av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
svsInfo("", QString::asprintf("Output: srate:%dHz fmt:%s chlayout:%s\n",
                              (int) outlink->sample_rate,
                              (char *) av_x_if_null(av_get_sample_fmt_name((AVSampleFormat) outlink->format), "?"),
                              args))
return 0;
}

以及过滤器用法:

AVFrame* resampleAudio(const QString& key, AVFrame *frame) {

    /* Push the decoded frame into the filtergraph */
    qint32 ret;
    ret = av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF);
    if(ret < 0) {
        svsWarning(key, QString("Error adding frame to buffer: %1").arg(svsAvErrorToFormattedString(ret)))
        // Delete input frame and return null
        av_frame_unref(frame);
        return nullptr;
    }

    AVFrame *resampled_frame = av_frame_alloc();

    /* Pull filtered frames from the filtergraph */
    ret = av_buffersink_get_frame(buffersink_ctx, resampled_frame);

    /* Set the timestamp on the resampled frame */
    resampled_frame->best_effort_timestamp = resampled_frame->pts;

    if(ret < 0) {
        // This is very common. For 48KHz -> 44.1KHz for some input frames the
        // filter has not data enough to generate another one.
        av_frame_unref(frame);
        av_frame_unref(resampled_frame);
        return nullptr;
    }
    av_frame_unref(frame);
    return resampled_frame;
}

在重新采样的帧上设置 best_effort_timestamp 使其正常工作很重要.但是此帧的PTS由滤波器设置.

Its important to set the best_effort_timestamp on the resampled frame to make it work. But the PTS of this frame is set by the filter.