[FFmpeg-devel] [PATCH 1/2] avfilter: add ff_inlink_peek_samples and ff_inlink_skip samples

[Paul B Mahol]

Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
 libavfilter/avfilter.c | 96 ++++++++++++++++++++++++++++++++++++++++++
 libavfilter/filters.h  | 17 ++++++++
 2 files changed, 113 insertions(+)

diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 394811916d..90c73fb64b 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -1190,6 +1190,61 @@ static int take_samples(AVFilterLink *link, unsigned min, unsigned max,
     return 0;
 }
 
+static int peek_samples(AVFilterLink *link, unsigned peek_samples,
+                        AVFrame **rframe)
+{
+    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(link, link->min_samples));
+    frame0 = frame = ff_framequeue_peek(&link->fifo, 0);
+    if (!link->fifo.samples_skipped && frame->nb_samples == peek_samples) {
+        *rframe = av_frame_clone(frame);
+        return 0;
+    }
+    nb_frames = 0;
+    nb_samples = 0;
+    while (1) {
+        if (nb_samples + frame->nb_samples >= peek_samples)
+            break;
+        nb_samples += frame->nb_samples;
+        nb_frames++;
+        if (nb_frames == ff_framequeue_queued_frames(&link->fifo))
+            break;
+        frame = ff_framequeue_peek(&link->fifo, nb_frames);
+    }
+
+    buf = ff_get_audio_buffer(link, peek_samples);
+    if (!buf)
+        return AVERROR(ENOMEM);
+    ret = av_frame_copy_props(buf, frame0);
+    if (ret < 0) {
+        av_frame_free(&buf);
+        return ret;
+    }
+    buf->pts = frame0->pts;
+
+    p = 0;
+    for (i = 0; i < nb_frames; i++) {
+        frame = ff_framequeue_peek(&link->fifo, i);
+        av_samples_copy(buf->extended_data, frame->extended_data, p, 0,
+                        frame->nb_samples, link->channels, link->format);
+        p += frame->nb_samples;
+    }
+    if (p < peek_samples) {
+        unsigned n = peek_samples - p;
+        frame = ff_framequeue_peek(&link->fifo, i);
+        av_samples_copy(buf->extended_data, frame->extended_data, p, 0, n,
+                        link->channels, link->format);
+    }
+
+    *rframe = buf;
+    return 0;
+}
+
 static int ff_filter_frame_to_filter(AVFilterLink *link)
 {
     AVFrame *frame = NULL;
@@ -1512,6 +1567,47 @@ int ff_inlink_consume_samples(AVFilterLink *link, unsigned min, unsigned max,
     return 1;
 }
 
+int ff_inlink_peek_samples(AVFilterLink *link, unsigned nb_samples,
+                           AVFrame **rframe)
+{
+    AVFrame *frame;
+    int ret;
+
+    av_assert1(nb_samples);
+    *rframe = NULL;
+    if (!ff_inlink_check_available_samples(link, nb_samples))
+        return 0;
+    if (link->status_in)
+        nb_samples = FFMIN(nb_samples, ff_framequeue_queued_samples(&link->fifo));
+    ret = peek_samples(link, nb_samples, &frame);
+    if (ret < 0)
+        return ret;
+    *rframe = frame;
+    return !!frame;
+}
+
+void ff_inlink_skip_samples(AVFilterLink *link, unsigned skip_samples)
+{
+    while (skip_samples > 0) {
+        AVFrame *frame = ff_inlink_peek_frame(link, 0);
+        if (skip_samples >= frame->nb_samples) {
+            frame = ff_framequeue_take(&link->fifo);
+            skip_samples -= frame->nb_samples;
+            av_frame_free(&frame);
+        } else {
+            break;
+        }
+    }
+
+    if (skip_samples)
+        ff_framequeue_skip_samples(&link->fifo, skip_samples, link->time_base);
+
+    if (ff_inlink_queued_frames(link)) {
+        AVFrame *frame = ff_inlink_peek_frame(link, 0);
+        consume_update(link, frame);
+    }
+}
+
 AVFrame *ff_inlink_peek_frame(AVFilterLink *link, size_t idx)
 {
     return ff_framequeue_peek(&link->fifo, idx);
diff --git a/libavfilter/filters.h b/libavfilter/filters.h
index 1157755403..7dc0b35981 100644
--- a/libavfilter/filters.h
+++ b/libavfilter/filters.h
@@ -115,6 +115,23 @@ int ff_inlink_consume_frame(AVFilterLink *link, AVFrame **rframe);
 int ff_inlink_consume_samples(AVFilterLink *link, unsigned min, unsigned max,
                             AVFrame **rframe);
 
+/**
+ * Peek samples from the link's FIFO.
+ *
+ * @return  >0 if a samples are available,
+ *          0 and set rframe to NULL if no samples are available,
+ *          or AVERROR code
+ */
+int ff_inlink_peek_samples(AVFilterLink *link, unsigned nb_samples,
+                           AVFrame **rframe);
+
+/**
+ * Skip samples from the link's FIFO.
+ *
+ * @note  May trigger process_command() and/or update is_disabled.
+ */
+void ff_inlink_skip_samples(AVFilterLink *link, unsigned skip);
+
 /**
  * Access a frame in the link fifo without consuming it.
  * The first frame is numbered 0; the designated frame must exist.
-- 
2.17.1