Zencoder Encoding Settings: Audio Processing

Product(s)
Zencoder
Role(s)
API Developer
Topic(s)
Audio
Encoding Settings
API(s)
Zencoder API

This topic contains details for encoding settings related to audio processing. For other audio-specific settings, see audio and Rate Control.

audio_gain

audio_gain:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A number between -60 and 60

Compatible Job Types: All

Example: 5

Description:

Apply a gain amount to the audio. This increases or decreases the volume of the audio by the specified amount after applying other effects. This is mainly useful for adjusting the levels after applying other effects, or making adjustments to files for which you already know the level. Sounds that go just a bit over the max volume will be gently limited to preserve fidelity, but increasing significantly over the maximum volume will result in distorted sound. See audio_normalize for automatically increasing volume without distortion. Specified in dB, either positive or negative, up to 60dB.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_gain": 5
    }
  ]
}

See Also: audio_normalize

audio_normalize

audio_normalize:Boolean

API Versions: V1, V2

Parent: outputs

Default: false

Valid Values: true or false

Compatible Job Types: vod

Example: true

Description:

Normalize audio to 0dB. This increases the volume of the audio as much as possible without causing distortion. To help ensure consistent adjustment by the expansion and compression effects, we normalize the volume both before and after those effects. See audio_pre_normalize and audio_post_normalize to only normalize at one of those points. audio_normalize is equivalent to specifying both audio_pre_normalize and audio_post_normalize.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_normalize": true
    }
  ]
}

See Also: audio_gain, audio_pre_normalize, and audio_post_normalize

audio_pre_normalize

audio_pre_normalize:Boolean

API Versions: V1, V2

Parent: outputs

Default: false

Valid Values: true or false

Compatible Job Types: All

Example: true

Description:

Normalize the audio before applying expansion or compression effects. See audio_normalize for more information.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_pre_normalize": true
    }
  ]
}

See Also: audio_gain, audio_normalize, and audio_post_normalize

audio_post_normalize

audio_post_normalize:Boolean

API Versions: V1, V2

Parent: outputs

Default: false

Valid Values: true or false

Compatible Job Types: All

Example: true

Description:

Normalize the audio after applying expansion or compression effects. See audio_normalize for more information.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_post_normalize": true
    }
  ]
}

See Also: audio_gain, audio_normalize, and audio_pre_normalize

audio_bass

audio_bass:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A number of decibels, from -10 to 10

Compatible Job Types: All

Example: 2

Description:

Increase or decrease the amount of bass in the audio, similar to a stereo’s tone controls. Specified in dB, positive or negative amounts up to 10.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_bass": 2
    }
  ]
}

See Also: audio_treble

audio_treble

audio_treble:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A number of decibels, from -10 to 10

Compatible Job Types: All

Example: 2

Description:

Increase or decrease the amount of treble in the audio, similar to a stereo’s tone controls. Specified in dB, positive or negative amounts up to 10.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_treble": 2
    }
  ]
}

See Also: audio_bass

audio_highpass

audio_highpass:Integer

API Versions: V1, V2

Parent: outputs

Valid Values: A frequency in Hz, from 5 to 24000

Compatible Job Types: All

Example: 10

Description:

Apply a high-pass filter to the audio at the specified frequency in Hz. This will prevent audio frequencies below the specified threshold from being included in the output. A very common use of this setting is to reduce rumble/noise from audio, such as the sounds of trucks driving by outside during the recording or some sounds caused by wind or hitting a microphone. DC-Shift can also be reduced/removed by specifying a high-pass filter at a low frequency, such as 10 Hz.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_highpass": 10
    }
  ]
}

See Also: audio_lowpass

audio_lowpass

audio_lowpass:Integer

API Versions: V1, V2

Parent: outputs

Valid Values: A frequency in Hz, from 5 to 24000

Compatible Job Types: All

Example: 3000

Description:

Apply a low-pass filter to the audio at the specified frequency in Hz. This will prevent audio frequencies above the specified threshold from being included in the output. This can be used to cut out very high pitched whine sounds from audio, or to create special effects, such as a "telephone" setting (using audio_highpass of 300 and audio_lowpass of 3000).

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_lowpass": 3000
    }
  ]
}

See Also: audio_highpass

audio_compression_ratio

audio_compression_ratio:Float

API Versions: V1, V2

Parent: outputs

Valid Values: 1.0 to 30.0

Compatible Job Types: All

Example: 2.5

Description:

Compress the dynamic range of the audio by reducing volume at a specified ratio of N:1, above the specified audio_compression_threshold. Ratios between 1.0 and 30.0 are valid. Compression is essentially useful to make the audio volume more consistent between quiet points and loud points. This can be used to make loud spots (yelling, or slammed doors, etc.) less jarring. Used in conjunction with audio_gain or audio_normalization, it can make quiet parts of a speech more audible.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_compression_ratio": 2.5
    }
  ]
}

See Also: audio_compression_threshold

audio_compression_threshold

audio_compression_threshold:Float

API Versions: V1, V2

Parent: outputs

Default: -20

Valid Values: A negative number between 0 and -120

Compatible Job Types: All

Example: -30

Description:

Set the threshold above which audio compression is applied, when audio_compression_ratio is specified. Values are specified in dB as a negative number down to -120.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_compression_threshold": -30
    }
  ]
}

See Also: audio_compression_ratio

audio_expansion_ratio

audio_expansion_ratio:Float

API Versions: V1, V2

Parent: outputs

Valid Values: 1.0 to 30.0

Compatible Job Types: All

Example: 2.5

Description:

Expand the dynamic range of the audio by reducing volume at a specified ratio of N:1, below the specified audio_expansion_threshold. Ratios between 1.0 and 30.0 are valid. Expansion is essentially useful for reducing unwanted sounds during quiet points, or making the difference between loud and quiet sounds more significant.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_expansion_ratio": 2.5
    }
  ]
}

See Also: audio_expansion_threshold

audio_expansion_threshold

audio_expansion_threshold:Float

API Versions: V1, V2

Parent: outputs

Default: -35

Valid Values: A negative number between 0 and -120

Compatible Job Types: All

Example: -10

Description:

Set the threshold below which audio compression is applied, when audio_expansion_ratio is specified. Values are specified in dB as a negative number down to -120.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_expansion_threshold": -10
    }
  ]
}

See Also: audio_expansion_ratio

audio_fade

audio_fade:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A positive number, up to 30.0

Compatible Job Types: All

Example: 10

Description:

Apply fade-in and fade-out effects to the audio with the specified duration in seconds. Equivalent to specifying both audio_fade_in and audio_fade_out with this duration.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_fade": 10
    }
  ]
}

See Also: audio_fade_in and audio_fade_out

audio_fade_in

audio_fade_in:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A positive number, up to 30.0

Compatible Job Types: All

Example: 10

Description:

Apply a fade-in effect to the audio with the specified duration in seconds.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_fade_in": 10
    }
  ]
}

See Also: audio_fade and audio_fade_out

audio_fade_out

audio_fade_out:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A positive number, up to 30.0

Compatible Job Types: vod

Example: 10

Description:

Apply a fade-out effect to the audio with the specified duration in seconds.

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_fade_out": 10
    }
  ]
}

See Also: audio_fade and audio_fade_in

audio_loudness_level

audio_loudness_level:Float

API Versions: V1, V2

Parent: outputs

Valid Values: A number of decibels, from -60.0 to 60.0

Compatible Job Types: vod

Example: -23

Description:

Adjust the loudness level of the audio. This is measured in LUFS and specified in dB. This is useful to set the output loudness level to conform to a standard (-23dB for EBU R.128)

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_loudness_level": -23
    }
  ]
}

audio_karaoke_mode

audio_karaoke_mode:Boolean

API Versions: V1, V2

Parent: outputs

Default: false

Valid Values: true or false

Compatible Job Types: All

Example: true

Description:

Apply a "karaoke" effect to the audio by subtracting the right audio channel from the left, and keeping only the difference. Only applies to stereo outputs.

Be careful using this this feature:

  • It sometimes produces distortion
  • It sometimes does nothing at all
  • It sometimes negatively affects the background noise or music
{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "audio_karaoke_mode": true
    }
  ]
}