Fraunhofer Logo

HTML5 AAC Audio Playback Tests - Metadata

Fraunhofer Institute for Integrated Circuits

General

This page tests if an HE-AAC or AAC-LC decoder correctly applies audio-specific metadata, including program reference level, dynamic range control and downmixing. It consists of a number of AAC bitstreams, designed in a way that allows for a rough verification of these features by simply listening to the decoder output.

Test 1: Program Reference Level

Audio 1kHz sine wave
Test This item tests if the decoder applies the program reference level
Expected Output If the decoder correctly applies the program reference level, the 1kHz tone is output at a constant level (short dropouts may be noticeable every second when PRL changes). If the decoder does not apply the program reference level, the level of the tone changes every second.

Stereo AAC-LC

Stereo HE-AAC

Multichannel AAC-LC

Multichannel HE-AAC

Test 2: MPEG Dynamic Range Control (DRC)

Audio 1kHz sine wave
Test This item tests if the decoder applies MPEG dynamic range control. For this test the decoder has to be configured to apply full DRC (no scaling of DRC coefficients).
Expected Output If the decoder correctly applies DRC, the 1kHz tone is output at a constant level (short dropouts may be noticeable every second when DRC gain changes). If the decoder does not apply DRC, the level of the tone changes every second.

Stereo AAC-LC

Stereo HE-AAC

Multichannel AAC-LC

Multichannel HE-AAC

Test 3: MPEG Multiband (DRC)

Audio sine waves
Test This item tests if the decoder applies MPEG multiband dynamic range control. For this
test the decoder should be configured to apply full DRC (no scaling of DRC coefficients).
Expected Output If the decoder correctly applies multiband DRC, a constant tone is output (short dropouts may be noticeable every second when DRC gains change). If the decoder does not apply multiband DRC, the tone changes every second.

Stereo AAC-LC

Stereo HE-AAC

Multichannel AAC-LC

Multichannel HE-AAC

Test 4: ETSI Heavy Compression

Audio 1kHz sine wave
Test This item tests if the decoder applies ETSI heavy compression DRC. For this test the decoder has to be configured to apply heavy compression.
Expected Output If the decoder correctly applies heavy compression, the 1kHz tone is output at a constant level (short dropouts may be noticeable every second when DRC gain changes). If the decoder does not apply heavy compression, the level of the tone changes every second.

Stereo AAC-LC

Stereo HE-AAC

Multichannel AAC-LC

Multichannel HE-AAC

Test 5: MPEG Mixdown Coefficient

Audio White noise in front channels, 1kHz sine wave in rear channels
Test This item tests if the decoder applies 5.1 to stereo downmixing using the MPEG PCE mixdown coefficient. For this test the decoder has to be configured to apply stereo downmixing.
Expected Output If the decoder correctly applies the mixdown coefficient, the the output signal – a mix of white noise and a 1kHz tone – has a constant level, with an interruption of the tone for one second after three seconds (short dropouts may be noticeable every second when the mixdown coefficient changes). If the decoder does not apply the mixdown coefficient, the level of the 1kHz tone changes every second.

Multichannel AAC-LC

Multichannel HE-AAC

Test 6: ETSI Downmix Coefficients

Audio White noise in front channels, 1kHz sine wave in rear channels
Test This item tests if the decoder applies 5.1 to stereo downmixing using the ETSI center and surround downmix coefficients. For this test the decoder has to be configured to apply stereo downmixing.
Expected Output If the decoder correctly applies the downmix coefficients, the the output signal – a mix of white noise and a 1kHz tone – has a constant level, with an interruption of the tone for one second after seven seconds (short dropouts may be noticeable every second when the downmix coefficient changes). If the decoder does not apply the downmix coefficients, the level of the 1kHz tone changes every second.

Multichannel AAC-LC

Multichannel HE-AAC

Troubleshooting

While TV's and AV Receivers have supported metadata for decades for receiving broadcast content, many web browsers, digital media adapters, and some phones and tablets do not apply metadata during decoding of IP-delivered content. Thus, on these latter devices the bitstreams may play, but without metadata support.

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