Here is an MP3 converter / decoder library based on jLayer which is released under the LGPL license see the link for requirements.
The library is in two parts:
A converter that will convert an MP3 file to a WAV file, the resulting file specifications are determined from the source file. It is common that non 44100Hz stereo WAV files fail to play on android devices. If a converted file won't play it is likely that the original source file was not 44100Hz stereo. This library does not allow modifications to the sample rate or number of channels. I haven't tested it's speed against warwounds liblame decoder, I expect that the jlayer converter will be slower, but it's here for completeness as it's in the jLayer library.
A decoder which converts the MP3 by MP3 frames that can be stored in a byte array which allows the results to be streamed to AudioTrack for playing. The decoder returns PCM stereo samples so you could also recreate a WAV file with the appropriate header file.
The attached demo shows one method for streaming the MP3 using AudioTrack. This is by neccessity CPU intensive and may not work well on older devices. I have tested it on a Sony Experia SP which handles it very well, and an older Stealth Hydro Tablet which seems to provide acceptable performance.
Library documentation:
SLMP3
Author: Steve Laming
Version: 1.2
Xml Document converted with warwounds B4A library reference generator
The decoding processes are blocking, so should be run in a separate thread.
Uncompressed audio files can be huge, the SLByteArrayBuffer is used to allow constant resizing of the buffer to stop it growing too large and causing out of memory errors.
Streaming
There are two options for streaming a file, from the beginning to the end (Initialize), or by time (Initialize2) specifying a start and end time in milliseconds. As the decoder works in frames the played times may not be totally accurate, but to the nearest frame, this will probably be unnoticable in most scenarios.
For the streaming itself, it is possible to set the number of frames that the encoder will process in a single call. This needs to be fairly low as once the AudioTrack starts playing it needs a constant flow of data to play glitch free. To reduce the memory usage, the output buffer is managed and limited to a size of 200000 bytes.
The Demo
The demo app shows both streaming options which simply use alternative initialization methods.
An input stream is required to feed the decoder, the demo reads the MP3 file into an array and creates the input stream from there. MP3 files are not normally that large and most songs should not provide an array that is too large. if you have problems using large MP3 files an alternative method of creating the inputstream may be required.
Seek
V1.2 of the library introduces a seekTo, this only seeks forward from the current play point.
V1.1 of the demo implements a seek back by re-initializing the file then calling seekTo with an imperceptible delay. It may be noticeable on very large files if the seek is near the end.
Demo Requirements:
mp3streams
Download and unzip the xml and jar files to your additional libraries directory.
For the demo: ensure that the required libraries (see above) are installed and selected.
SLMP3 V1.0 superseded.
SLMP3 V1.1 superseded.
SLMP3 V1.2 attached. - Added methods to GetSampleFrequency and GetNoChannels from the decoder and SeekTo.
mp3streamdemo V1.1 attached:
Mp3Test V1.0 attached
10/11/2013 SLMP3 updated removed documentation errors.
The library is in two parts:
A converter that will convert an MP3 file to a WAV file, the resulting file specifications are determined from the source file. It is common that non 44100Hz stereo WAV files fail to play on android devices. If a converted file won't play it is likely that the original source file was not 44100Hz stereo. This library does not allow modifications to the sample rate or number of channels. I haven't tested it's speed against warwounds liblame decoder, I expect that the jlayer converter will be slower, but it's here for completeness as it's in the jLayer library.
A decoder which converts the MP3 by MP3 frames that can be stored in a byte array which allows the results to be streamed to AudioTrack for playing. The decoder returns PCM stereo samples so you could also recreate a WAV file with the appropriate header file.
The attached demo shows one method for streaming the MP3 using AudioTrack. This is by neccessity CPU intensive and may not work well on older devices. I have tested it on a Sony Experia SP which handles it very well, and an older Stealth Hydro Tablet which seems to provide acceptable performance.
Library documentation:
SLMP3
Author: Steve Laming
Version: 1.2
- SLConvertMP3
Events:- Finished
- Convert (eventName As String, sourceFile As String, destFile As String)
Convert sourcefile(MP3) to destfile (WAV)
- SLStreamMP3
Methods:- GetNoChannels As Int
- GetSampleFrequency As Int
- Initialize (inpStream As InputStream)
Initialize to read from inpStream - Initialize2 (inpStream As InputStream, startMs As Long, endMs As Long)
Initialize to read from inpStream
And positions at the first frame in inpstream to be decoded and streamed
The decoder works on frames so the ms times returned may not be exact - SeekTo (seekPos As Long)
Seek to seekPos, it will only seek forwards.
See the demo app for how to seek backwards. - Stream (noFrames As Int) As Byte[]
Return the output from the next decoded noFrames - currPos As Float
get the current play position in ms
Xml Document converted with warwounds B4A library reference generator
The decoding processes are blocking, so should be run in a separate thread.
Uncompressed audio files can be huge, the SLByteArrayBuffer is used to allow constant resizing of the buffer to stop it growing too large and causing out of memory errors.
Streaming
There are two options for streaming a file, from the beginning to the end (Initialize), or by time (Initialize2) specifying a start and end time in milliseconds. As the decoder works in frames the played times may not be totally accurate, but to the nearest frame, this will probably be unnoticable in most scenarios.
For the streaming itself, it is possible to set the number of frames that the encoder will process in a single call. This needs to be fairly low as once the AudioTrack starts playing it needs a constant flow of data to play glitch free. To reduce the memory usage, the output buffer is managed and limited to a size of 200000 bytes.
The Demo
The demo app shows both streaming options which simply use alternative initialization methods.
An input stream is required to feed the decoder, the demo reads the MP3 file into an array and creates the input stream from there. MP3 files are not normally that large and most songs should not provide an array that is too large. if you have problems using large MP3 files an alternative method of creating the inputstream may be required.
Seek
V1.2 of the library introduces a seekTo, this only seeks forward from the current play point.
V1.1 of the demo implements a seek back by re-initializing the file then calling seekTo with an imperceptible delay. It may be noticeable on very large files if the seek is near the end.
Demo Requirements:
mp3streams
- AudioTrack Library
- Dialogs Library
- RandomAccessFile Library
- SLByteArrayBuffer Library
- SLMP3 Library
- Threading Library
- SLMP3Library
Download and unzip the xml and jar files to your additional libraries directory.
For the demo: ensure that the required libraries (see above) are installed and selected.
SLMP3 V1.0 superseded.
SLMP3 V1.1 superseded.
- MP3 convert now runs in an async stream so you don't need to run it in a thread.
- Added _Finished callback.
SLMP3 V1.2 attached. - Added methods to GetSampleFrequency and GetNoChannels from the decoder and SeekTo.
mp3streamdemo V1.1 attached:
Updated demo to allow skipping of the MP3. and get SampleRate and
no channels from the decoder.
no channels from the decoder.
Mp3Test V1.0 attached
10/11/2013 SLMP3 updated removed documentation errors.
Attachments
Last edited:
