Function take_samples

libavfilter/avfilter.c:1129–1188

}

static int take_samples(FilterLinkInternal *li, unsigned min, unsigned max,
                        AVFrame **rframe)
{
    FilterLink *l = &li->l;
    AVFilterLink *link = &l->pub;
    AVFrame *frame0, *frame, *buf;
    unsigned nb_samples, nb_frames, i, p;
    int ret;

    /* Note: this function relies on no format changes and must only be
       called with enough samples. */
    av_assert1(samples_ready(li, l->min_samples));
    frame0 = frame = ff_framequeue_peek(&li->fifo, 0);
    if (!li->fifo.samples_skipped && frame->nb_samples >= min && frame->nb_samples <= max) {
        *rframe = ff_framequeue_take(&li->fifo);
        return 0;
    }
    nb_frames = 0;
    nb_samples = 0;
    while (1) {
        if (nb_samples + frame->nb_samples > max) {
            if (nb_samples < min)
                nb_samples = max;
            break;
        }
        nb_samples += frame->nb_samples;
        nb_frames++;
        if (nb_frames == ff_framequeue_queued_frames(&li->fifo))
            break;
        frame = ff_framequeue_peek(&li->fifo, nb_frames);
    }

    buf = ff_get_audio_buffer(link, nb_samples);
    if (!buf)
        return AVERROR(ENOMEM);
    ret = av_frame_copy_props(buf, frame0);
    if (ret < 0) {
        av_frame_free(&buf);
        return ret;
    }

    p = 0;
    for (i = 0; i < nb_frames; i++) {
        frame = ff_framequeue_take(&li->fifo);
        av_samples_copy(buf->extended_data, frame->extended_data, p, 0,
                        frame->nb_samples, link->ch_layout.nb_channels, link->format);
        p += frame->nb_samples;
        av_frame_free(&frame);
    }
    if (p < nb_samples) {
        unsigned n = nb_samples - p;
        frame = ff_framequeue_peek(&li->fifo, 0);
        av_samples_copy(buf->extended_data, frame->extended_data, p, 0, n,
                        link->ch_layout.nb_channels, link->format);
        ff_framequeue_skip_samples(&li->fifo, n, link->time_base);
    }

    *rframe = buf;