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.
Note that this page does not test the MPEG-D DRC metadata introduced for use with xHE-AAC
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.