avfilter: add loop filters

Signed-off-by: Paul B Mahol <onemda@gmail.com>

2 files changed, 41 insertions, 0 deletions

diff --git a/libavutil/audio_fifo.c b/libavutil/audio_fifo.c
index d5298cce4d..e4d38e0524 100644
--- a/libavutil/audio_fifo.c
+++ b/libavutil/audio_fifo.c
@@ -155,6 +155,30 @@ int av_audio_fifo_peek(AVAudioFifo *af, void **data, int nb_samples)
     return nb_samples;
 }
 
+int av_audio_fifo_peek_at(AVAudioFifo *af, void **data, int nb_samples, int offset)
+{
+    int i, ret, size;
+
+    if (offset < 0 || offset >= af->nb_samples)
+        return AVERROR(EINVAL);
+    if (nb_samples < 0)
+        return AVERROR(EINVAL);
+    nb_samples = FFMIN(nb_samples, af->nb_samples);
+    if (!nb_samples)
+        return 0;
+    if (offset > af->nb_samples - nb_samples)
+        return AVERROR(EINVAL);
+
+    offset *= af->sample_size;
+    size = nb_samples * af->sample_size;
+    for (i = 0; i < af->nb_buffers; i++) {
+        if ((ret = av_fifo_generic_peek_at(af->buf[i], data[i], offset, size, NULL)) < 0)
+            return AVERROR_BUG;
+    }
+
+    return nb_samples;
+}
+
 int av_audio_fifo_read(AVAudioFifo *af, void **data, int nb_samples)
 {
     int i, ret, size;
diff --git a/libavutil/audio_fifo.h b/libavutil/audio_fifo.h
index 24f91dab72..d8a9194a8d 100644
--- a/libavutil/audio_fifo.h
+++ b/libavutil/audio_fifo.h
@@ -111,6 +111,23 @@ int av_audio_fifo_write(AVAudioFifo *af, void **data, int nb_samples);
 int av_audio_fifo_peek(AVAudioFifo *af, void **data, int nb_samples);
 
 /**
+ * Peek data from an AVAudioFifo.
+ *
+ * @see enum AVSampleFormat
+ * The documentation for AVSampleFormat describes the data layout.
+ *
+ * @param af          AVAudioFifo to read from
+ * @param data        audio data plane pointers
+ * @param nb_samples  number of samples to peek
+ * @param offset      offset from current read position
+ * @return            number of samples actually peek, or negative AVERROR code
+ *                    on failure. The number of samples actually peek will not
+ *                    be greater than nb_samples, and will only be less than
+ *                    nb_samples if av_audio_fifo_size is less than nb_samples.
+ */
+int av_audio_fifo_peek_at(AVAudioFifo *af, void **data, int nb_samples, int offset);
+
+/**
  * Read data from an AVAudioFifo.
  *
  * @see enum AVSampleFormat