# tf.signal.idct

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| [![](https://www.tensorflow.org/images/GitHub-Mark-32px.png) View source on GitHub](https://github.com/tensorflow/tensorflow/blob/v2.10.1/tensorflow/python/ops/signal/dct_ops.py#L181-L224) |

Computes the 1D [Inverse Discrete Cosine Transform (DCT)](https://en.wikipedia.org/wiki/Discrete_cosine_transform#Inverse_transforms) of `input`.

#### View aliases


**Compat aliases for migration**

See
[Migration guide](https://www.tensorflow.org/guide/migrate) for
more details.

[`tf.compat.v1.signal.idct`](https://www.tensorflow.org/api_docs/python/tf/signal/idct), [`tf.compat.v1.spectral.idct`](https://www.tensorflow.org/api_docs/python/tf/signal/idct)

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    tf.signal.idct(
        input, type=2, n=None, axis=-1, norm=None, name=None
    )

Currently Types I, II, III, IV are supported. Type III is the inverse of
Type II, and vice versa.

Note that you must re-normalize by 1/(2n) to obtain an inverse if `norm` is
not `'ortho'`. That is:
`signal == idct(dct(signal)) * 0.5 / signal.shape[-1]`.
When `norm='ortho'`, we have:
`signal == idct(dct(signal, norm='ortho'), norm='ortho')`.

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| ## Args ||
|---|---|
| `input` | A `[..., samples]` `float32`/`float64` `Tensor` containing the signals to take the DCT of. |
| `type` | The IDCT type to perform. Must be 1, 2, 3 or 4. |
| `n` | For future expansion. The length of the transform. Must be `None`. |
| `axis` | For future expansion. The axis to compute the DCT along. Must be `-1`. |
| `norm` | The normalization to apply. `None` for no normalization or `'ortho'` for orthonormal normalization. |
| `name` | An optional name for the operation. |

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| ## Returns ||
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| A `[..., samples]` `float32`/`float64` `Tensor` containing the IDCT of `input`. ||

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| ## Raises ||
|---|---|
| `ValueError` | If `type` is not `1`, `2` or `3`, `n` is not `None,`axis`is not`-1`, or`norm`is not`None`or`'ortho'\`. |

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## scipy compatibility

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Equivalent to [scipy.fftpack.idct](https://docs.scipy.org/doc/scipy-1.4.0/reference/generated/scipy.fftpack.idct.html)
for Type-I, Type-II, Type-III and Type-IV DCT.

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