avfilter: add showfreqs filter

4 files changed, 71 insertions, 0 deletions

diff --git a/libavutil/audio_fifo.c b/libavutil/audio_fifo.c
index 574907aa32..d5298cce4d 100644
--- a/libavutil/audio_fifo.c
+++ b/libavutil/audio_fifo.c
@@ -136,6 +136,25 @@ int av_audio_fifo_write(AVAudioFifo *af, void **data, int nb_samples)
     return nb_samples;
 }
 
+int av_audio_fifo_peek(AVAudioFifo *af, void **data, int nb_samples)
+{
+    int i, ret, size;
+
+    if (nb_samples < 0)
+        return AVERROR(EINVAL);
+    nb_samples = FFMIN(nb_samples, af->nb_samples);
+    if (!nb_samples)
+        return 0;
+
+    size = nb_samples * af->sample_size;
+    for (i = 0; i < af->nb_buffers; i++) {
+        if ((ret = av_fifo_generic_peek(af->buf[i], data[i], 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 d21e6a1318..d93be2aeb0 100644
--- a/libavutil/audio_fifo.h
+++ b/libavutil/audio_fifo.h
@@ -94,6 +94,22 @@ int av_audio_fifo_realloc(AVAudioFifo *af, int nb_samples);
 int av_audio_fifo_write(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
+ * @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(AVAudioFifo *af, void **data, int nb_samples);
+
+/**
  * Read data from an AVAudioFifo.
  *
  * @see enum AVSampleFormat
diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index f2fe93de75..07fb4ec811 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -148,6 +148,32 @@ int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size,
     return total - size;
 }
 
+int av_fifo_generic_peek(AVFifoBuffer *f, void *dest, int buf_size,
+                         void (*func)(void *, void *, int))
+{
+// Read memory barrier needed for SMP here in theory
+    uint8_t *rptr = f->rptr;
+    uint32_t rndx = f->rndx;
+
+    do {
+        int len = FFMIN(f->end - f->rptr, buf_size);
+        if (func)
+            func(dest, f->rptr, len);
+        else {
+            memcpy(dest, f->rptr, len);
+            dest = (uint8_t *)dest + len;
+        }
+// memory barrier needed for SMP here in theory
+        av_fifo_drain(f, len);
+        buf_size -= len;
+    } while (buf_size > 0);
+
+    f->rptr = rptr;
+    f->rndx = rndx;
+
+    return 0;
+}
+
 int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size,
                          void (*func)(void *, void *, int))
 {
diff --git a/libavutil/fifo.h b/libavutil/fifo.h
index f3bdcbceb4..0e4070b99e 100644
--- a/libavutil/fifo.h
+++ b/libavutil/fifo.h
@@ -85,6 +85,16 @@ int av_fifo_space(const AVFifoBuffer *f);
 
 /**
  * Feed data from an AVFifoBuffer to a user-supplied callback.
+ * Similar as av_fifo_gereric_read but without discarding data.
+ * @param f AVFifoBuffer to read from
+ * @param buf_size number of bytes to read
+ * @param func generic read function
+ * @param dest data destination
+ */
+int av_fifo_generic_peek(AVFifoBuffer *f, void *dest, int buf_size, void (*func)(void*, void*, int));
+
+/**
+ * Feed data from an AVFifoBuffer to a user-supplied callback.
  * @param f AVFifoBuffer to read from
  * @param buf_size number of bytes to read
  * @param func generic read function