Encodec (#991)

* initial encodec

* works

* nits

* use fast group norm

* fix for rnn layer

* fix mlx version

* use custom LSTM kernel

* audio encodec

* fix example, support batched inference

* nits

encodec/test.py

@@ -0,0 +1,66 @@
+# Copyright © 2024 Apple Inc.
+
+import mlx.core as mx
+import numpy as np
+import torch
+from datasets import Audio, load_dataset
+from transformers import AutoProcessor, EncodecModel
+from utils import load, load_audio, preprocess_audio
+
+
+def compare_processors():
+    np.random.seed(0)
+    audio_length = 95500
+    audio = np.random.uniform(size=(2, audio_length)).astype(np.float32)
+
+    processor = AutoProcessor.from_pretrained("facebook/encodec_48khz")
+
+    pt_inputs = processor(
+        raw_audio=audio, sampling_rate=processor.sampling_rate, return_tensors="pt"
+    )
+    mx_inputs = preprocess_audio(
+        mx.array(audio).T,
+        processor.sampling_rate,
+        processor.chunk_length,
+        processor.chunk_stride,
+    )
+
+    assert np.array_equal(pt_inputs["input_values"], mx_inputs[0].moveaxis(2, 1))
+    assert np.array_equal(pt_inputs["padding_mask"], mx_inputs[1])
+
+
+def compare_models():
+    pt_model = EncodecModel.from_pretrained("facebook/encodec_48khz")
+    mx_model, _ = load("mlx-community/encodec-48khz-float32")
+
+    np.random.seed(0)
+    audio_length = 190560
+    audio = np.random.uniform(size=(1, audio_length, 2)).astype(np.float32)
+    mask = np.ones((1, audio_length), dtype=np.int32)
+    pt_encoded = pt_model.encode(
+        torch.tensor(audio).moveaxis(2, 1), torch.tensor(mask)[None]
+    )
+    mx_encoded = mx_model.encode(mx.array(audio), mx.array(mask))
+    pt_codes = pt_encoded.audio_codes.numpy()
+    mx_codes = mx_encoded[0]
+    assert np.array_equal(pt_codes, mx_codes), "Encoding codes mismatch"
+
+    for mx_scale, pt_scale in zip(mx_encoded[1], pt_encoded.audio_scales):
+        if mx_scale is not None:
+            pt_scale = pt_scale.numpy()
+            assert np.allclose(pt_scale, mx_scale, atol=1e-3, rtol=1e-4)
+
+    pt_audio = pt_model.decode(
+        pt_encoded.audio_codes, pt_encoded.audio_scales, torch.tensor(mask)[None]
+    )
+    pt_audio = pt_audio[0].squeeze().T.detach().numpy()
+    mx_audio = mx_model.decode(*mx_encoded, mx.array(mask))
+    mx_audio = mx_audio.squeeze()
+    assert np.allclose(
+        pt_audio, mx_audio, atol=1e-4, rtol=1e-4
+    ), "Decoding audio mismatch"
+
+
+if __name__ == "__main__":
+    compare_processors()
+    compare_models()