Zencoder Encoding Settings: AAC

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 AAC audio.

Notes

You may find that some of your videos the outputs are a few milliseconds longer than the inputs with black frames added at the end. The reason for this is a longer audio duration due to the fact that any time you encode aac, extra audio priming samples are added to the beginning of the audio stream. (See this Apple document for more details.) For HLS outputs, we adjust the audio duration to account for the samples.

max_aac_profile

max_aac_profile:String

API Versions: V1, V2

Parent: outputs

Default: he-aac

Valid Values: aac-lc, he-aac, or he-aac-v2

Compatible Job Types: All

Example: he-aac-v2

Description:

The AAC audio codec has several profiles. By default, Zencoder will pick the right profile based on the bitrate and number of channels used: stereo content under 40kbps will use HE-AAC v2 if max-aac-profile is set to "he-aac-v2"; stereo content under 84kbps will use HE-AAC if max-aac-profile is set to "he-aac"; and AAC-LC will be used for higher bitrate content, or if max-aac-profile is set to "aac-lc". "he-aac" is the default value, which means that by default, 0-84kbps will use HE-AAC and 85kbps and up will use AAC-LC.

AAC-LC ("Low Complexity") is the most common AAC profile, and virtually every AAC decoder supports AAC-LC. AAC-LC allows mono and stereo, with sample rates from 8khz-96khz, and high bitrates (>300kbps). Use AAC-LC when encoding stereo content at 80kbps and above or mono content above 40kbps, or when you want to support devices that only play AAC-LC, like the Roku or old iPods.

HE-AAC ("High Efficiency") is a widely supported AAC profile that sounds better than AAC-LC at low bitrates by implementing Spectral Band Replication (SBR). HE-AAC supports mono and stereo content at sample rates of 16khz-48khz and bitrates ranging from 16kbps-128kbps. Most web and mobile decoders support HE-AAC, including Flash, HTML5 (wherever AAC is supported), iPhone, iPad, Android, etc. Use HE-AAC for stereo content below 80, or low bitrate mono content.

HE-AAC v2 is optimized for even more aggressive compression than HE-AAC by adding Parametric Stereo (PS) to HE-AAC. This means that HE-AAC v2 is only suitable for stereo content; mono content can only use HE-AAC. HE-AAC v2 is supported by Flash, HTML5, and some mobile devices (Windows Phone 7, Android). Use HE-AAC v2 for stereo content below 40kbps or so, but not for iOS audio. (Newer iOS devices can play HE-AAC v2 content, but ignore the PS information, resulting in mono content.)

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "max_aac_profile": "he-aac-v2"
    }
  ]
}

See Also: force_aac_profile

force_aac_profile

force_aac_profile:String

API Versions: V1, V2

Parent: outputs

Valid Values: aac-lc, he-aac, or he-aac-v2

Compatible Job Types: All

Example: he-aac-v2

Description:

Force the use of a particular AAC profile, rather than letting Zencoder choose the best profile for the bitrate.

The AAC audio codec has several profiles.

AAC-LC ("Low Complexity") is the most common AAC profile, and virtually every AAC decoder supports AAC-LC. AAC-LC allows mono and stereo, with sample rates from 8khz-96khz, and high bitrates (>300kbps). Use AAC-LC when encoding stereo content at 80kbps and above or mono content above 40kbps, or when you want to support devices that only play AAC-LC, like the Roku or old iPods.

HE-AAC ("High Efficiency") is a widely supported AAC profile that sounds better than AAC-LC at low bitrates by implementing Spectral Band Replication (SBR). HE-AAC supports mono and stereo content at sample rates of 16khz-48khz and bitrates ranging from 16kbps-128kbps. Most web and mobile decoders support HE-AAC, including Flash, HTML5 (wherever AAC is supported), iPhone, iPad, Android, etc. Use HE-AAC for stereo content below 80, or low bitrate mono content.

HE-AAC v2 is optimized for even more aggressive compression than HE-AAC by adding Parametric Stereo (PS) to HE-AAC. This means that HE-AAC v2 is only suitable for stereo content; mono content can only use HE-AAC. HE-AAC v2 is supported by Flash, HTML5, and some mobile devices (Windows Phone 7, Android). Use HE-AAC v2 for stereo content below 40kbps or so, but not for iOS audio. (Newer iOS devices can play HE-AAC v2 content, but ignore the PS information, resulting in mono content.)

{
  "input": "s3://zencodertesting/test.mov",
  "outputs": [
    {
      "force_aac_profile": "he-aac-v2"
    }
  ]
}

See Also: max_aac_profile