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https://github.com/arkq/openaptx
Reverse-engineered apt-X audio codec
https://github.com/arkq/openaptx
aptx aptx-hd library reverse-engineering
Last synced: about 2 months ago
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Reverse-engineered apt-X audio codec
- Host: GitHub
- URL: https://github.com/arkq/openaptx
- Owner: arkq
- License: mit
- Created: 2017-11-01T10:31:14.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2022-12-17T23:19:25.000Z (about 2 years ago)
- Last Synced: 2024-07-02T20:45:19.848Z (6 months ago)
- Topics: aptx, aptx-hd, library, reverse-engineering
- Language: C
- Homepage:
- Size: 471 KB
- Stars: 134
- Watchers: 16
- Forks: 20
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# [open]aptx - reverse-engineered apt-X
This project is for research purposes only. Without a proper license private and commercial usage
might be a case of a patent infringement. If you are looking for a library, which can be installed
and used legally (commercial, private and educational usage), go to the Qualcomm® aptX™
[homepage](https://www.aptx.com/) and contact Qualcomm customer service.
The source code itself is licensed under the terms of the MIT license. However, compression
algorithms are patented and licensed under the terms of a proprietary license. Hence, compilation
and redistribution in a binary format is forbidden!
## Compilation
```sh
mkdir build && cd build
cmake -DENABLE_DOC=ON -DWITH_FFMPEG=ON -DWITH_SNDFILE=ON ..
make && make install
```
### Configure options
- `ENABLE_DOC` - build and install manual files (requires Doxygen)
- `ENABLE_APTX_DECODER_API` - build with apt-X / apt-X HD decoder API (default: ON)
- `ENABLE_APTX_ENCODER_API` - build with apt-X / apt-X HD encoder API (default: ON)
- `ENABLE_APTX422` - build reverse engineered apt-X library based on `bt-aptX-x86-4.2.2.so`
- `ENABLE_APTXHD100` - build reverse engineered apt-X HD library based on `aptXHD-1.0.0-ARMv7A`
- `WITH_FFMPEG` - use FFmpeg as a back-end (otherwise, stub library will be built)
- `WITH_SNDFILE` - read file formats supported by libsndfile (used by openaptx utils)
In the apt-X stub library (build without FFmpeg back-end), all symbols are exported as
[weak](https://en.wikipedia.org/wiki/Weak_symbol). As a consequence, it should be possible to
overwrite them during runtime with other library which exports strong symbols. However, it might
be required to define `LD_DYNAMIC_WEAK` environment variable - for more information consult
`ld.so` manual.
When reverse-engineered libraries were enabled, they will be automatically linked with the apt-X
stub library (build without FFmpeg back-end). See previous paragraph for the meaning of this.
## Benchmark
Below is the result of a small benchmark test performed with various apt-X encoding libraries.
Test was done with the usage of `aptxenc` and `aptxhdenc` tools from this repository.
Elapsed user time was calculated with the usage of a standard UNIX `time` command line tool. All
libraries (except original Qualcomm libraries) were compiled with Clang version 8.0.7 with the
`O2` or `O3` optimization level.
### Setup
- CPU: ARM Cortex-A53
- Input file: WAV audio, Microsoft PCM, 16 bit, stereo 48000 Hz
- Input duration: 15 minutes 45 seconds
### Results
| Library | apt-X | Mbit/s | apt-X HD | Mbit/s |
|----------------------------------------|-----------|---------|-----------|---------|
| [libaptX-1.0.16-rel-Android21][1] | 1m00.370s | 1.23673 | — | — |
| [libaptXHD-1.0.1-rel-Android21][1] | — | — | 1m07.030s | 1.11109 |
| openaptx-stub | 0m04.480s | 0.0 | 0m04.820s | 0.0 |
| openaptx-ffmpeg (libavcodec-58.54.100) | 1m58.100s | 0.60835 | 2m03.270s | 0.58354 |
| aptx422 | 1m19.840s | 0.91721 | — | — |
| aptxHD100 | — | — | 1m21.950s | 0.89616 |
| [libopenaptx-0.2.0][2] | 1m22.090s | 0.89062 | 1m25.730s | 0.85429 |
[1]: ./archive "Archive with Qualcomm apt-X encoding libraries"
[2]: https://github.com/pali/libopenaptx "The apt-X encoder/decoder based on FFmpeg code"
## Resources
1. [AptX audio codec family](https://en.wikipedia.org/wiki/AptX)
2. [Method and apparatus for electrical signal coding](https://www.google.com/patents/EP0398973B1?cl=en)
3. [Two-channel QMF bank](https://www.hindawi.com/journals/isrn/2013/815619/)