aud22_18.yaml

- en: StreamWriter Basic Usage
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- en: 原文：[https://pytorch.org/audio/stable/tutorials/streamwriter_basic_tutorial.html](https://pytorch.org/audio/stable/tutorials/streamwriter_basic_tutorial.html)
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- en: Note
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- en: Click [here](#sphx-glr-download-tutorials-streamwriter-basic-tutorial-py) to
    download the full example code
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- en: '**Author**: [Moto Hira](mailto:moto%40meta.com)'
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- en: This tutorial shows how to use [`torchaudio.io.StreamWriter`](../generated/torchaudio.io.StreamWriter.html#torchaudio.io.StreamWriter
    "torchaudio.io.StreamWriter") to encode and save audio/video data into various
    formats/destinations.
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- en: Note
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- en: This tutorial requires FFmpeg libraries. Please refer to [FFmpeg dependency](../installation.html#ffmpeg-dependency)
    for the detail.
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- en: Warning
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- en: TorchAudio dynamically loads compatible FFmpeg libraries installed on the system.
    The types of supported formats (media format, encoder, encoder options, etc) depend
    on the libraries.
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- en: To check the available muxers and encoders, you can use the following command
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- en: '[PRE0]'
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  zh: '[PRE0]'
- en: Preparation[](#preparation "Permalink to this heading")
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  prefs:
  - PREF_H2
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- en: '[PRE1]'
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  zh: '[PRE1]'
- en: '[PRE2]'
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  zh: '[PRE2]'
- en: '[PRE3]'
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  zh: '[PRE3]'
- en: The basic usage[](#the-basic-usage "Permalink to this heading")
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- en: To save Tensor data into media formats with StreamWriter, there are three necessary
    steps
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- en: Specify the output
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  - PREF_OL
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- en: Configure streams
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  - PREF_OL
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- en: Write data
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- en: The following code illustrates how to save audio data as WAV file.
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- en: '[PRE4]'
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  zh: '[PRE4]'
- en: '[PRE5]'
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- en: '[PRE6]'
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- en: '[PRE7]'
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  zh: '[PRE7]'
- en: null
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- en: Your browser does not support the audio element.
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- en: Now we look into each step in more detail.
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- en: Write destination[](#write-destination "Permalink to this heading")
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- en: StreamWriter supports different types of write destinations
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- en: Local files
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  - PREF_OL
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- en: File-like objects
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  - PREF_OL
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- en: Streaming protocols (such as RTMP and UDP)
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  - PREF_OL
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- en: Media devices (speakers and video players) †
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  - PREF_OL
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- en: † For media devices, please refer to [StreamWriter Advanced Usages](./streamwriter_advanced.html).
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- en: Local files[](#local-files "Permalink to this heading")
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  - PREF_H3
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- en: StreamWriter supports saving media to local files.
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- en: '[PRE8]'
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- en: This works for still images and videos as well.
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- en: '[PRE9]'
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  zh: '[PRE9]'
- en: File-like objects[](#file-like-objects "Permalink to this heading")
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- en: You can also pass a file-lie object. A file-like object must implement `write`
    method conforming to [`io.RawIOBase.write`](https://docs.python.org/3/library/io.html#io.RawIOBase.write
    "(in Python v3.12)").
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- en: '[PRE10]'
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- en: '[PRE11]'
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- en: Streaming protocols[](#streaming-protocols "Permalink to this heading")
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- en: You can stream the media with streaming protocols
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- en: '[PRE12]'
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  zh: '[PRE12]'
- en: Configuring output streams[](#configuring-output-streams "Permalink to this
    heading")
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- en: Once the destination is specified, the next step is to configure the streams.
    For typical audio and still image cases, only one stream is required, but for
    video with audio, at least two streams (one for audio and the other for video)
    need to be configured.
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- en: Audio Stream[](#audio-stream "Permalink to this heading")
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  - PREF_H3
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- en: An audio stream can be added with `add_audio_stream()` method.
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- en: For writing regular audio files, at minimum `sample_rate` and `num_channels`
    are required.
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- en: '[PRE13]'
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- en: By default, audio streams expect the input waveform tensors to be `torch.float32`
    type. If the above case, the data will be encoded into the detault encoding format
    of WAV format, which is 16-bit signed integer Linear PCM. StreamWriter converts
    the sample format internally.
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- en: If the encoder supports multiple sample formats and you want to change the encoder
    sample format, you can use `encoder_format` option.
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- en: In the following example, the StreamWriter expects the data type of the input
    waveform Tensor to be `torch.float32`, but it will convert the sample to 16-bit
    signed integer when encoding.
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- en: '[PRE14]'
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- en: If the data type of your waveform Tensor is something other than `torch.float32`,
    you can provide `format` option to change the expected data type.
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- en: The following example configures StreamWriter to expect Tensor of `torch.int16`
    type.
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- en: '[PRE15]'
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- en: The following figure illustrates how `format` and `encoder_format` options work
    for audio streams.
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- en: '![https://download.pytorch.org/torchaudio/tutorial-assets/streamwriter-format-audio.png](../Images/cc11e30ca877aed22f85b963e3d21750.png)'
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- en: Video Stream[](#video-stream "Permalink to this heading")
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- en: To add a still image or a video stream, you can use `add_video_stream()` method.
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- en: At minimum, `frame_rate`, `height` and `width` are required.
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- en: '[PRE16]'
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- en: For still images, please use `frame_rate=1`.
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- en: '[PRE17]'
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- en: Similar to the audio stream, you can provide `format` and `encoder_format` option
    to controll the format of input data and encoding.
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- en: The following example encodes video data in YUV422 format.
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- en: '[PRE18]'
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- en: YUV formats are commonly used in video encoding. Many YUV formats are composed
    of chroma channel of different plane size than that of luma channel. This makes
    it difficult to directly express it as `torch.Tensor` type. Therefore, StreamWriter
    will automatically convert the input video Tensor into the target format.
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- en: StreamWriter expects the input image tensor to be 4-D (time, channel, height,
    width) and `torch.uint8` type.
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- en: The default color channel is RGB. That is three color channels corresponding
    red, green and blue. If your input has different color channel, such as BGR and
    YUV, you can specify it with `format` option.
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- en: The following example specifies BGR format.
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- en: '[PRE19]'
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- en: The following figure illustrates how `format` and `encoder_format` options work
    for video streams.
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- en: '![https://download.pytorch.org/torchaudio/tutorial-assets/streamwriter-format-video.png](../Images/dae3b96285e227e70b2ff53781bc191c.png)'
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- en: Write data[](#write-data "Permalink to this heading")
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- en: Once streams are configured, the next step is to open the output location and
    start writing data.
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- en: Use `open()` method to open the destination, and then write data with `write_audio_chunk()`
    and/or `write_video_chunk()`.
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- en: Audio tensors are expected to have the shape of (time, channels), and video/image
    tensors are expected to have the shape of (time, channels, height, width).
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- en: Channels, height and width must match the configuration of the corresponding
    stream, specified with `"format"` option.
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- en: Tensor representing a still image must have only one frame in time dimension,
    but audio and video tensors can have arbitral number of frames in time dimension.
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- en: The following code snippet illustrates this;
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- en: Ex) Audio[](#ex-audio "Permalink to this heading")
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  - PREF_H3
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- en: '[PRE20]'
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  zh: '[PRE20]'
- en: Ex) Image[](#ex-image "Permalink to this heading")
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  - PREF_H3
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- en: '[PRE21]'
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  zh: '[PRE21]'
- en: Ex) Video without audio[](#ex-video-without-audio "Permalink to this heading")
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- en: '[PRE22]'
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  zh: '[PRE22]'
- en: Ex) Video with audio[](#ex-video-with-audio "Permalink to this heading")
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- en: To write video with audio, separate streams have to be configured.
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- en: '[PRE23]'
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- en: Writing data chunk by chunk[](#writing-data-chunk-by-chunk "Permalink to this
    heading")
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- en: When writing data, it is possible to split data along time dimension and write
    them by smaller chunks.
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- en: '[PRE24]'
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- en: Example - Spectrum Visualizer[](#example-spectrum-visualizer "Permalink to this
    heading")
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- en: In this section, we use StreamWriter to create a spectrum visualization of audio
    and save it as a video file.
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- en: To create spectrum visualization, we use [`torchaudio.transforms.Spectrogram`](../generated/torchaudio.transforms.Spectrogram.html#torchaudio.transforms.Spectrogram
    "torchaudio.transforms.Spectrogram"), to get spectrum presentation of audio, generate
    raster images of its visualization using matplotplib, then use StreamWriter to
    convert them to video with the original audio.
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- en: '[PRE28]'
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- en: Prepare Data[](#prepare-data "Permalink to this heading")
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- en: First, we prepare the spectrogram data. We use [`Spectrogram`](../generated/torchaudio.transforms.Spectrogram.html#torchaudio.transforms.Spectrogram
    "torchaudio.transforms.Spectrogram").
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- en: We adjust `hop_length` so that one frame of the spectrogram corresponds to one
    video frame.
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- en: '[PRE29]'
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- en: The resulting spectrogram looks like the following.
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- en: '[PRE30]'
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- en: '![streamwriter basic tutorial](../Images/23bb162fe5e2ad4ea90d1784cca151d1.png)'
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- en: Prepare Canvas[](#prepare-canvas "Permalink to this heading")
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- en: We use `matplotlib` to visualize the spectrogram per frame. We create a helper
    function that plots the spectrogram data and generates a raster imager of the
    figure.
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- en: '[PRE31]'
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  zh: '[PRE31]'
- en: Write Video[](#write-video "Permalink to this heading")
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- en: Finally, we use StreamWriter and write video. We process one second of audio
    and video frames at a time.
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- en: '[PRE32]'
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  zh: '[PRE32]'
- en: '[PRE33]'
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  zh: '[PRE33]'
- en: Result[](#result "Permalink to this heading")
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  zh: 结果[](#result "跳转到此标题的永久链接")
- en: The result looks like below.
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  zh: 结果如下所示。
- en: '[PRE34]'
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  zh: '[PRE34]'
- en: 
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- en: Your browser does not support the video tag.
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  zh: 您的浏览器不支持视频标签。
- en: Carefully watching the video, it can be observed that the sound of “s” (curio**si**ty,
    be**si**des, thi**s**) has more energy allocated on higher frequency side (right
    side of the video).
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  zh: 仔细观察视频，可以发现“s”音的声音（curio**si**ty, be**si**des, thi**s**）在高频侧（视频的右侧）有更多的能量分配。
- en: 'Tag: [`torchaudio.io`](../io.html#module-torchaudio.io "torchaudio.io")'
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  zh: 标签：[`torchaudio.io`](../io.html#module-torchaudio.io "torchaudio.io")
- en: '**Total running time of the script:** ( 0 minutes 6.918 seconds)'
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  zh: '**脚本的总运行时间：**（0分钟6.918秒）'
- en: '[`Download Python source code: streamwriter_basic_tutorial.py`](../_downloads/d8d57badf5e878c5beb8d32b0aefc7dd/streamwriter_basic_tutorial.py)'
  id: totrans-127
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  zh: '[`下载Python源代码：streamwriter_basic_tutorial.py`](../_downloads/d8d57badf5e878c5beb8d32b0aefc7dd/streamwriter_basic_tutorial.py)'
- en: '[`Download Jupyter notebook: streamwriter_basic_tutorial.ipynb`](../_downloads/78e5305a9c1fa517857bc0197643e56d/streamwriter_basic_tutorial.ipynb)'
  id: totrans-128
  prefs: []
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  zh: '[`下载Jupyter笔记本：streamwriter_basic_tutorial.ipynb`](../_downloads/78e5305a9c1fa517857bc0197643e56d/streamwriter_basic_tutorial.ipynb)'
- en: '[Gallery generated by Sphinx-Gallery](https://sphinx-gallery.github.io)'
  id: totrans-129
  prefs: []
  type: TYPE_NORMAL
  zh: '[Sphinx-Gallery生成的图库](https://sphinx-gallery.github.io)'