Update README

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

README.md

@@ -19,7 +19,9 @@ This pipeline extracts features of a given audio file using a VGGish model imple
 
 The Operator returns a list of named tuple `[NamedTuple('AudioOutput', [('vec', 'ndarray')])]` containing following fields:
 
-- each item in the output list represents for embedding(s) for an audio clip, which depends on `time-window` in [yaml](./audio_embedding_vggish.yaml).
+- each item in the output list represents for embedding(s) for an audio clip,
+length & timestamps of which depend on `time-window` in [yaml](./audio_embedding_vggish.yaml) 
+(You can modify `time_range_sec` & `time_step_sec` to change the way of audio split.)
 
 - vec:
   - embeddings of input audio
@@ -42,9 +44,14 @@ $ pip3 install towhee
 >>> from towhee import pipeline
 
 >>> embedding_pipeline = pipeline('towhee/audio-embedding-vggish')
->>> embedding = embedding_pipeline('/path/to/your/audio')
+>>> outs = embedding_pipeline('/path/to/your/audio')
+>>> embeds = outs[0][0]
 ```
 
 ## How it works
 
-This pipeline includes a main operator type [audio-embedding](https://towhee.io/operators?limit=30&page=1&filter=3%3Aaudio-embedding) (default: [towhee/torch-vggish](https://hub.towhee.io/towhee/torch-vggish)). The pipeline first decodes the input audio file into audio frames and then combine frames depending on time-window configs. The audio-embedding operator takes combined frames as input and generate corresponding audio embeddings.
+This pipeline includes two main operator types:
+[audio-decode](https://towhee.io/operators?limit=30&page=1&filter=1%3Aaudio-decode) & [audio-embedding](https://towhee.io/operators?limit=30&page=1&filter=3%3Aaudio-embedding).
+By default, the pipeline uses [towhee/audio-decoder](https://towhee.io/towhee/audio-decoder) to load audio path as a list of audio frames in ndarray.
+Then `time-window` will combine audio frames into a list of ndarray, each of which represents an audio clip in fixed length.
+At the end, the [towhee/torch-vggish](https://hub.towhee.io/towhee/torch-vggish)) operator will generate a list of audio embeddings for each audio clip.