Android Question How to set OutputFormat of AudioStreamer

[tigrot]

Hi everybody
I don't know which is is the class which serves as base for AudioStreamer. If it is MediaRecorder I wonder if it possible to set the encoder to something different from PCM, just to save bandwidth.
I don't see methods or properties exposing such a capability.
I use AudioStreamer to send(and receive) audio via 3G network, but I get unstable results, expecially on transmission.
Thank you
Mauro

 

[Erel]

AudioStreamer output is PCM. It cannot be changed automatically. It is based on AudioRecord which only supports PCM.

 

[tigrot]

So this is not the correct "route" to take if I need to stream compressed audio over the Internet.
Is AudioStreamer the only library capable of streaming audio from mike to the Internet?

Thank you for prompt help. We'd be lost without you.

Mauro

 

[Erel]

There is at least one other library that records audio. However it most probably uses the same Android API so the output will be PCM as well.

Have you tried to compress the stream with gzip (CompressedStreams from RandomAccessFile)?

 

[tigrot]

I did, it works, but since the 3G is asimmetric, I get a small bandwidth for upload, so I have to shrink the stream to minimum term. Now it works well only HDSPA or similar connections, good in towns, but outside it's good for ingoing connections like WEB navigation. Also rapid changes in network speed create buffer full situations. I was in telephony since 1990, I have written PABX's firmware, but VOIP swept my experience away. I have also many CTI applications, but only with POTS for extensions. Digital Trunks like E1 are my only digital experience.
If I have time I'll write (or port) a stream compressor... Hope that it won't kill the phone!

 

[tigrot]

Hi Erel, the issue is that zip and GZIP are text compression, working with binary data produced a small compression(to 90-95% of original buffer).
Any idea?


Ciao
Mauro

 

[Erel]

Have you tried one of the mp3 encoder libraries: http://www.b4x.com/android/forum/pages/results/?query=mp3+encoder&page=1&prefix=0

 

[tigrot]

I'm giving a look, but MP3 has a minimum stamp of 8Kb/sec. I think to resample to 8bits instead of 16bits so I can cut stream size to 50%. I'm developing a wrapper for Lame... ,

 

[tigrot]

After some day of study I have written a GSM library module to send a compressed stream. Now delay is only 1'' and bandwidth is only a 20%. I have published the library. Now the APP is actually in release state. Thank you Erel for strong support!