HE-AAC Channel ID

This bitstream contains:

Spoken Channel Identification in English

BLITS (EBU Tech 3304-4.1)

EBU Multichannel Ident (EBU Tech 3304-4.2)

Narration in the following channels: FL FC FR RS LS



HE-AAC Bitstream:

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Original Wave File:

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AAC-LC Channel ID

This is the test above encoded in AAC-LC. Note this is 320 kb/s, not 160 as announced.

AAC Bitstream:

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HE-AAC Channel ID - With H.264 Video

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This is the bitstream above multiplexed with an explanatory graphic encoded in H.264 Main Profile at 800x600 resolution.

LFE and SBR Test

This tests for proper bass management and reproduction of the SBR portion of the HE-AAC bitstream.

This bitstream contains:

Bass Management - 63 Hz tone @ -18 dBFS, 2 seconds Left Front Center Right Front Right Suround Left Surround LFE (@ -28dBFS)

SBR - 6, 8, 10, 12 kHz tones @ -18 dBFS, 0.5 seconds each Left Front Center Right Front Right Suround Left Surround

Spoken Channel Identification in English

Narration: Center channel

There is a 1 kHz -18 dBFS tone in the center channel throughout.

AAC Bitstream:

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Original Wave File:

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If a subwoofer is used with limited-range main speakers, all 60 Hz tones should play at the same level through the subwoofer. (Hold SLM next to subwoofer) If full-range speakers are used, the 60 Hz tones should play through each speaker individually, though levels may vary due to standing wave or resonances in the listening rrom. The LFE signal is encoded 10 dB lower to account for the 10 dB gain in the LFE channel in the playback amplifer's bass management circuits.

If the decoder supports SBR, all four tones, 6, 8, 10, and 12 KHz should be heard (or seen on a sound level meter if you have high-frequency hearing loss). If the decoder is only decoding the AAC-LC portion of the bitstream, only the first two tones will be heard. This is at the encoded bitrate of 160 kb/s, at other bitrates the SBR crossover frequency used by the encoder will vary, resulting in more or less tones being heard. Missing tones in only one channel may indicate a speaker problem.

LFE and SBR Test - With H.264 Video

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This is the bitstream above multiplexed with an explanatory graphic encoded in H.264 Main Profile at 800x600 resolution.

Troubleshooting

The MPEG-4 AAC audio bitstreams above are presented as HTML5 audio objects - which should play back correctly in:

Microsoft Internet Explorer 9+ (Win 7+ PC)

Apple Safari 5+ (Win 7+ PC)

Google Chrome (Win 7+ PC, Mac OS, Android)

when your computer has 5.1 channel speakers connected or connects via HDMI to a 5.1 or better surround sound AVR or home theater system. Note that many browsers and media players (particularly on mobile devices such as the iPhone) will output a stereo downmix from these streams, even if they don't support multichannel output.

The bitstream files, if downloaded locally, should also play correctly in:

Microsoft Windows Media Player 12 (Win 7+ PC)

Apple QuickTime (Win 7+ PC or Mac)

VLC Player (Win 7+ PC)

No sound or no rear channels? Check the troubleshooting page.

7.1 Channel Support

The AAC codec family has supported up to 48 channels of audio since its initial development through predefined channel configurations and a flexible escape mechanism. The predefined channel configurations from the 2005 version of the AAC standard are shown below, along with the additional configurations standardized in Amendment 4 of the AAC standard in 2013 shown in cyan tint:

Channel Configuration

Value Channnels Speaker Mapping Common Use 0 Escape Code 1 1 Center Mono 2 2 Left, Right Stereo 3 3 Center, Left, Right 4 4 Center, Left, Right, Surround 5 5 ITU BS.775-1 6 5.1 ITU BS.775-1 5.1 Surround 7 7.1 SDDS 8-10 Reserved Value 11 6.1 12 7.1 7.1 (a) of ITU BS.2159 Blu-ray 13 Reserved Value 14 7.1 Top 7.1 (d) of ITU BS.2159 15 Reserved Value

This channel configuration value is specified in the AudioSpecificConfig structure of the AAC bitstream. When the channel configuration value is set to 0, the channel configuration is not predefined, but is explicitly described in the Program Config Element structure. This allows arbitrary channel configurations to be used. (For information on these structures, refer to the Fraunhofer Application Bulletin AAC Transport Formats or to the MPEG AAC standard: ISO/IEC 14496-3.)

Supplying the 7.1 configuration with the PCE escape method was necessary since the only predefined 7.1 configuration was the theatrical SDDS speaker configuration of five front speakers and two surround speakers. Thus, the more common BluRay 7.1 configuration with three front speakers and four surround speakers was specified using the PCE structure.

An amendment (ISO/IEC 14496-3:2009/Amd 4:2013) to the AAC standard also allows signalling the BluRay 7.1 configuration in the channel configuration field by using the value 12. An AAC decoder is also required to continue decoding configurations sent in the PCE.

More importantly, AAC lacked profiles requiring 7.1 support, with a level 4 or level 5 decoder only required to support 5.1 decoding. The amendment includes level 6 to require 7.1 decoding. Also, the amendment specifies a method for controlling the downmixing of 7.1 channels to 5.1 channels with controlled gains, much as the existing standard does for 5.1. The amendment also includes the extra loudness metadata currently specified in DVB into the AAC specification.

7.1 Channel Identification

Spoken Channel Identification per ISO/IEC 23001-8, 48 kHz sampling rate, AOT = 5, 224 kb/s, explicit signalling, backwards compatible, BluRay 7.1 configuration signaled with PCE.

AAC Bitstream:

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Original Wave File:

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Support of 7.1 channel bitstreams is relatively new and might not be available on many decoders. This bitstream is provided for verification of 7.1 decoder implementations.



As of 2017, Google Chrome is able to successfully play this bitstream on Windows 7 computers and Safari is able to successfully play this bitstream on Mac OS computers.