HTML5 AAC Audio Playback Tests -
xHE-AAC to AAC-LC Comparison Page
Fraunhofer Institute for Integrated Circuits
This page compares xHE-AAC to AAC-LC to show the improvements in coding efficiency and speech quality enabled by xHE-AAC. At higher bitrates such as 128 kb/s, the quality of AAC-LC will be similar to xHE-AAC, since they are both in the “transparent” bitrate range. As the bitrate is reduced, quality differences between the two codecs will begin to appear.
To enable playback with legacy browsers, and to show loudness and DRC effects, all the content on this page has been encoded with the listed codec and bitrate, decoded to PCM (uncompressed audio) at a target loudness level of -16 LKFS, and then re-encoded as AAC-LC at a high and transparent bitrate. Note that AAC loudness control is not mandatory and so most AAC content today is not loudness normalized.
Audio Quality Improvements
Improved Speech Quality
Since xHE-AAC includes dedicated speech coding tools, speech quality can be greatly improved at lower bitrates compared to legacy codecs.
Dramatic Film - Netflix “Meridian”
- Stereo version
- Property of Netflix, used with permission
- Listening Tip: Listen for improved bandwidth on the rain at 1:30 and 1:45 with xHE-AAC at the lower bitrates.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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Male Speech
- EBU Sound Quality Assessment Material, Track 50
- Male English Speech
- C414 cardioid at 65 cm, BBC drama studio, RT60 = 0.3 seconds at midband
- Narration: L+R Channels
- Listening tips: Make sure to wear headphones while listening. Notice how sibilants and fricatives ("s", "sh", "f" sounds) are much better preserved with xHE-AAC. Audio bandwidth is reduced for AAC-LC resulting in a dull, muffled sound at the lower bitrates. The “compare” tab allows quick comparsion of the quality of xHE-AAC at 24 kb/s to that of AAC-LC at 48 kb/s.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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32 kb/s, xHE-AAC
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32 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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compare, xHE-AAC at 24 kb/s
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compare, AAC-LC at 48 kb/s
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Female Speech
- EBU Sound Quality Assessment Material, Track 49
- Female English Speech
- C414 cardioid at 65 cm, BBC drama studio, RT60 = 0.3 seconds at midband
- Narration: L+R Channels
- Listening Tip: Make sure to wear headphones while listening. Notice how sibilants and fricatives ("s", "sh", "f" sounds) are much better preserved with xHE-AAC. Audio bandwidth is reduced for AAC-LC resulting in a dull, muffled sound at the lower bitrates. The “compare” tab allows quick comparsion of the quality of xHE-AAC at 24 kb/s to that of AAC-LC at 48 kb/s.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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32 kb/s, xHE-AAC
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32 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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compare, xHE-AAC at 24 kb/s
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compare, AAC-LC at 48 kb/s
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Original Wave Files:
The SQAM test items are the property of the European Broadcast Union and may be downloaded from their website at https://tech.ebu.ch/publications/sqamcd
Transient and Audio Bandwidth Improvement
Music: “Rain”
- Rain
- Artist/Composer: Navajiva
- Licensed from Klangarchiv
- Listening Tips: Onsets of the picked guitar are much improved for xHE-AAC. For AAC-LC, the harmonic structure of the guitar notes erodes, leading to an "out of tune" sound. There is also warbling or reverb of the guitar on the first phrases.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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32 kb/s, xHE-AAC
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32 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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Music: “Walking”
- Walking Throughout The City
- Artist/Composer: Marc Rosenberger
- Licensed from Klangarchiv
- Listening Tips: xHE-AAC offers more audio bandwidth. Listen to the percussion, particularly the steady shaker in the background.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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32 kb/s, xHE-AAC
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32 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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Stereo Image Improvement
Music: “Farewell”
- “The Farewell”
- Artist/Composer: Albrecht “Abi” Linden
- Licensed from Klangarchiv
- Listening Tips: For AAC-LC the piano passages between the vocal parts are warbling and seem “unstable”. At 48kb/s for AAC-LC the vocals start sounding metallic and unnatural.
24 kb/s, xHE-AAC
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24 kb/s, AAC-LC
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32 kb/s, xHE-AAC
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32 kb/s, AAC-LC
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48 kb/s, xHE-AAC
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48 kb/s, AAC-LC
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64 kb/s, xHE-AAC
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64 kb/s, AAC-LC
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128 kb/s, xHE-AAC
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128 kb/s, AAC-LC
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Video Quality Demonstration
On typical program material, xHE offers similar audio quality at half of the AAC bitrate, this allows the video bitrate to be increased to reduce video coding artifacts. This demonstration shows the quality improvement for low-bitrate video, such as might be distributed over older-generation mobile networks or to subscribers with low data caps.
Since most web browsers are not able to decode HEVC or xHE-AAC, the files are decoded and re-encoded with AVC and AAC-LC at high and transparent bitrates to avoid generational artifacts.
Documentary Film - Fraunhofer “Welcome to Berlin”
- Codec Set 1: HEVC at 50 kb/s, HE-AAC at 32 kb/s (82 kb/s total)
- Codec Set 2: HEVC at 64 kb/s, xHE-AAC at 16 kb/s (80 kb/s total)
- Video Encoding:
- Main Concept HEVC Encoder
- Main Profile, Level 2.1
- Raster: 426 x 240 pixels
- Frame Rate: 14.98 Hz
- Coding Performance:
- Set 1: Overall PSNR (A) 33.449 dB
- Set 2: Overall PSNR (A) 34.530 dB
Viewing Tips:
The stills below indicate some of the video artifacts that are reduced by the increased video bitrate possible with xHE-AAC
HEVC + HE-AAC - 82 kb/s total
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HEVC + xHE-AAC - 80 kb/s total
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