Speex dev - Apr 2010 - Decoded output buffer size

Hi,

in a VoIP application, the endpoint A send speex payload to B.
B doesn't know how A acquire audio, it only know that the channel is
narrowband so, how can B know the size of the output buffer to pass to
the speex_decode()?

Thanks,
Daniele.

Daniele Barzotti <daniele.barzotti at eurocomtel.com> writes:
> Hi,
>
> in a VoIP application, the endpoint A send speex payload to B.
> B doesn't know how A acquire audio, it only know that the channel is
> narrowband so, how can B know the size of the output buffer to pass to
> the speex_decode()?
Usually a buffer is one frame of data, and a frame is 20 milliseconds.
Since the sample rate is typically 8 kHz in narrowband mode, this
corresponds to a buffer size of 160 samples.

--Randy

>
> Thanks,
> Daniele.
> _______________________________________________
> Speex-dev mailing list
> Speex-dev at xiph.org
> http://lists.xiph.org/mailman/listinfo/speex-dev
>
-- 
Randy Yates                      % "She's sweet on Wagner-I think
she'd die for Beethoven.
Digital Signal Labs              %  She love the way Puccini lays down a tune,
and
mailto://yates at ieee.org          %  Verdi's always creepin' from her
room."
http://www.digitalsignallabs.com % "Rockaria", *A New World Record*,
ELO

Il 14/04/2010 14:37, Randy Yates wrote:
> 
> Usually a buffer is one frame of data, and a frame is 20 milliseconds.
> Since the sample rate is typically 8 kHz in narrowband mode, this
> corresponds to a buffer size of 160 samples.
Hi Randy, thanks for the reply.
So, suppose I encode an audio buffer (8000 kHz, MONO, float) of 640 PCM
frames.
In output I have 4 speex frame of 20 byte each that I put in a RPT
payload of 80 bytes:

UINT CSpeexCodec::Encode( float *inBuff,
                          const char**outBuff,
                          UINT BufferFrames )
{
  speex_encoder_ctl(spx_state_,
                    SPEEX_GET_FRAME_SIZE,
                    &spx_frame_size_);

  while (BufferFrames>0)
  {
    speex_bits_reset(&spx_bits_);
    speex_encode(spx_state_, inBuff, &spx_bits_);
    nbBytes += speex_bits_write(&spx_bits_,
                                spx_enc_frame_,
                                spx_frame_size_);
    inBuff+= spx_frame_size_;
    BufferFrames -= spx_frame_size_;
  }

  ..nbBytes is 80 bytes..
}


Now I send this packet over the network and, into the receiving side, I
need to recreate the original PCM buffer (640 frames).
But how can I know the size of each speex frame into a multiframe payload?


Daniele.