# Audio encoding parameters

| Parameter | Description                                                                                                                                                                         |
| :-------- | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Codec     | Specify the codec for the audio encoding. 'Passthrough' is not supported when audio input is uncompressed. For PCM or Dolby E Passthrough, select 'SMPTE302 / Dolby E Passthrough'. |

## Pass-through specific parameters

| Parameter                                   | Description                                                                                                                                                                                                                                                                                                                                                                                                 |
| :------------------------------------------ | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Insert audio frames on signal loss          | Generate audio frames according to the input loss management configured in Media processing tab (silence, 1kHz tone) when the input source is lost. **Note:** If you activate this option, associated monitoring statistics are available from the [Service statistics](/beam/live-encoder/monitor-statistics) (see example below).                                                                         |
| Glitch supression                           | Only available if **Insert audio frames on signal loss** is checked. Repeat 3 audio frames before enabling input loss audio frames generation.                                                                                                                                                                                                                                                              |
| Generate audio frames if no source at start | Only available if **Insert audio frames on signal loss** is checked. If the audio service is missing at startup, generate audio frames according to the input loss management configured in Media processing tab (silence, 1kHz tone). Frames may be encoded in a different codec from the real audio. **Note:** Applies to both use cases where Live Encoder is configured either with SDI or as IP input. |

![el encoding audio passthrough silence stats](/_machine-assets/a5fa873c6f90ba400a23e4720e21d6d7817b386417bb7abdb9ca8d03d43249dc.png)
_Example of audio silence generation statistics_

## SMPTE-302 / Dolby E Pass-through additional parameters

| Parameter  | Description                                                                                                            |
| :--------- | :--------------------------------------------------------------------------------------------------------------------- |
| Data Width | Data width of AES audio sample to be encoded. Possible values: **Follow input**, **16-bit**, **20-bit**, or **24-bit** |

## MPEG-1 Layer II, Dolby Digital, Dolby Digital Plus, AAC, HE-AAC, HE-AAC v2 parameters

| Parameter     | Description                                                                              |
| :------------ | :--------------------------------------------------------------------------------------- |
| Watermarking  | Type of watermarking insertion to use                                                    |
| Profile       | Profile to use with AAC codec                                                            |
| Channels mode | Number of audio channels in the encoded audio track                                      |
| Bit rate      | Bandwidth used to encode the audio stream                                                |
| Sampling rate | Number of audio samples per second defined in Hz                                         |
| Frame rate    | Frame rate as defined in video input                                                     |
| Blackout      | This blackout configuration will be applied to the related audio/video/subtitles stream. |

## Dolby Digital additional parameters

| Parameter             | Description                                                                                                                                                              |
| :-------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Dialog normalization  | Metadata parameter that controls playback gain. Possible values: **Auto** or, from **-1 dB** to **-31 dB.** **Auto** means that no processing will be done on the input. |
| Dolby Surround mode   | Decoders can use this flag to automatically switch on Pro Logic decoding.                                                                                                |
| DRC Line Mode Profile | The Dynamic Range Control restricts the signal's absolute peak level for a decoder using the line mode.                                                                  |
| DRC RF Mode Profile   | The Dynamic Range Control restricts the signal's absolute peak level for decoder using the RF mode.                                                                      |
| DC highpass filter    | A DCblocking 3Hz highpass filter applied on the main Dolby channel. Used to remove DC offsets in the program audio. Only switch off in exceptional circumstances.        |

**Related information**\
[Configure the audio encoding parameters](/beam/live-encoder/configure/encoding)