Speex dev - Apr 2010 - Decoded output buffer size

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Il 15/04/2010 01:30, Conrad Parker wrote:
>
>> But how can I know the size of each speex frame into a multiframe
payload?
> 
> use speex_bit_read_from() just once on the packet, then call
> speex_decode() once for each frame.
> 
> Conrad.
Thanks for the reply, Conrad.
What is not clear for me (and I didn't found it on the manual) is how to
decode a multi-frame payload.
Once have called speex_bits_read_from, I need a way to know how many
speex frames there are, how can I do this?

I try to use speex_bits_remaining, but after some cycles it returns
always 4.

UINT DecodePayload( char* payload, UINT payload_len )
{
  speex_bits_reset(&spx_bits_);
  speex_bits_read_from(&spx_bits_, payload, payload_len);
  UINT nbBytes = speex_bits_remaining(&spx_bits_);

  while (nbBytes>0)
  {
    speex_decode(spx_state_, &spx_bits_, spx_dec_frame_);
    nbBytes = speex_bits_remaining(&spx_bits_);

    // Save the speex frame into the buffer
    DecOutBuffer_.Write(spx_dec_frame_, spx_frame_size_);
  }
}

Any suggestion?

Thanks,
Daniele.
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On 15 April 2010 17:55, Daniele Barzotti
<daniele.barzotti at eurocomtel.com> wrote:
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> Hash: SHA1
>
> Il 15/04/2010 01:30, Conrad Parker wrote:
>>
>>> But how can I know the size of each speex frame into a multiframe
payload?
>>
>> use speex_bit_read_from() just once on the packet, then call
>> speex_decode() once for each frame.
>>
>> Conrad.
>
> Thanks for the reply, Conrad.
> What is not clear for me (and I didn't found it on the manual) is how
to
> decode a multi-frame payload.
> Once have called speex_bits_read_from, I need a way to know how many
> speex frames there are, how can I do this?
>
> I try to use speex_bits_remaining, but after some cycles it returns
> always 4.
>
> UINT DecodePayload( char* payload, UINT payload_len )
> {
> ?speex_bits_reset(&spx_bits_);
> ?speex_bits_read_from(&spx_bits_, payload, payload_len);
> ?UINT nbBytes = speex_bits_remaining(&spx_bits_);
>
> ?while (nbBytes>0)
> ?{
> ? ?speex_decode(spx_state_, &spx_bits_, spx_dec_frame_);
> ? ?nbBytes = speex_bits_remaining(&spx_bits_);
>
> ? ?// Save the speex frame into the buffer
> ? ?DecOutBuffer_.Write(spx_dec_frame_, spx_frame_size_);
> ?}
> }
>
> Any suggestion?
I think speex_decode() updates the number of bits remaining; here's what I
use:

http://git.xiph.org/?p=libfishsound.git;a=blob;f=src/libfishsound/speex.c;h=ac435cba37354d85c2852ce4c7c6305490c0d585;hb=HEAD#l342

but the number of frames in a packet is up to your application. For an
Ogg stream it will be a field in the speex_header, for RTP using SDP
it is calculated from ptime according to section 5.6 of RFC5574:
http://tools.ietf.org/rfc/rfc5574.txt
Without SDP, section 3.5 states:

  "The Speex decoder [SPEEX] can detect the bit-rate from the payload
   and is responsible for detecting the 20 msec boundaries between each
   frame."

but I don't know how that translates into libspeex calls. Jean-Marc?

Conrad.

Il 15/04/2010 11:17, Conrad Parker wrote:
> 
> but the number of frames in a packet is up to your application. 
> 
>   "The Speex decoder [SPEEX] can detect the bit-rate from the payload
>    and is responsible for detecting the 20 msec boundaries between each
>    frame."
Hi,
reading more careful the speex_decode() help (
http://www.speex.org/docs/api/speex-api-reference/group__Codec.html#g0ac60440b73e560fcfbca4f9e497d993
), it should be enough to test the return value: 0 for no error, -1 for
end of stream, -2 corrupt stream.

UINT DecodePayload( char* payload, UINT payload_len )
{
  speex_bits_reset(&spx_bits_);
  speex_bits_read_from(&spx_bits_, payload, payload_len);
  UINT nbBytes = speex_bits_remaining(&spx_bits_);


  while (nbBytes>0)
  {
    if ( speex_decode(spx_state_, &spx_bits_, spx_dec_frame_) != 0 )
      break;
    nbBytes = speex_bits_remaining(&spx_bits_);
    // Save the speex frame into the buffer
    DecOutBuffer_.Write(spx_dec_frame_, spx_frame_size_);
  }
}

Daniele.