Support resample

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

__init__.py

@@ -1,5 +1,5 @@
 from .audio_decoder_ffmpeg import AudioDecoderFFmpeg
 
 
-def ffmpeg(batch_size=-1):
-    return AudioDecoderFFmpeg(batch_size)
+def ffmpeg(**kwargs):
+    return AudioDecoderFFmpeg(**kwargs)

audio_decoder_ffmpeg.py

@@ -11,16 +11,29 @@ class AudioDecoderFFmpeg(PyOperator):
     """
     """
 
-    def __init__(self, batch_size=-1) -> None:
+    def __init__(self, batch_size=-1, sample_rate=None, layout=None) -> None:
         super().__init__()
         self._batch_size = batch_size
+        self._sample_rate = sample_rate
+        self._layout = layout
 
     def __call__(self, audio_path: str):
         frames = []
         in_container = av.open(audio_path)
         stream = in_container.streams.get(audio=0)[0]
+        if self._sample_rate or self._layout:
+            resampler = av.AudioResampler(
+                format=av.AudioFormat(stream.format.name).packed,
+                layout=self._layout if self._layout else 'mono',
+                rate=self._sample_rate if self._sample_rate else 8000
+                )
+        else:
+            resampler = None
+
         if self._batch_size <= 0:
             for frame in in_container.decode(stream):
+                if resampler:
+                    frame = resampler.resample(frame)[0]
                 timestamp = int(frame.time * 1000)
                 sample_rate = frame.sample_rate
                 layout = frame.layout.name
@@ -28,6 +41,8 @@ class AudioDecoderFFmpeg(PyOperator):
                 yield AudioFrame(ndarray, sample_rate, timestamp, layout)
         else:
             for frame in in_container.decode(stream):
+                if resampler:
+                    frame = resampler.resample(frame)[0]
                 timestamp = int(frame.time * 1000)
                 sample_rate = frame.sample_rate
                 layout = frame.layout.name