[Freeswitch-dev] Recompile mod_opus for 8KHz sampling rate

[Tamas Jalsovszky]

Is there any info how much  bandwidth is required for 48kHz audio? How CPU
hungry is downsampling to 8kHz G711?
According to opus-codec.org, opus can use sampling rates from 8kHz, not
just 48kHz. In cases when the call ends in PSTN, won't be appropriate to
support 8kHz sampling rate in FS too?


On Thu, Aug 1, 2013 at 9:18 PM, Anthony Minessale <
anthony.minessale at gmail.com> wrote:

> Opus always uses 48khz
> On Aug 1, 2013 2:15 PM, "Dimosthenis Arkoudeas" <dimosthenis at arkoudeas.com>
> wrote:
>
>>  Hi all,****
>>
>> ** **
>>
>> Playing with mod_opus came up with the following.****
>>
>> I am trying to recompile the codec with 8Khz and 40ms ptime. I am not
>> familiar with the codec internals and not really sure what parameters
>> should I change…****
>>
>> ** **
>>
>> In mod_opus.c :****
>>
>> ** **
>>
>> ** **
>>
>> Line 59:****
>>
>> int bitrate_bps = codec->implementation->bits_per_second;****
>>
>>                 int use_vbr = 1;****
>>
>>                 int complexity = 10;****
>>
>>                 int use_inbandfec = 1;****
>>
>>                 int use_dtx = 1;****
>>
>>                 int bandwidth = OPUS_BANDWIDTH_FULLBAND;****
>>
>>                 int err;****
>>
>> ** **
>>
>> I suppose that the bandwidth must be changed to OPUS_BANDWIDTH_NARROWBAND
>> and use_vbr=0 and I haven’t found yet whether the FEC parameter is passed
>> to opus encoder.****
>>
>> ** **
>>
>> And in Line 184 , I think the following parameters must be changed****
>>
>> ** **
>>
>>  switch_codec_interface_t *codec_interface;****
>>
>>         int samples = 480;****
>>
>>         int bytes = 960;****
>>
>>         int mss = 10000;****
>>
>>         int x = 0;****
>>
>>         int rate = 48000;****
>>
>>         int bits = 32000;****
>>
>> ** **
>>
>> ** **
>>
>> Can you propose any values about these parameters to achieve 8khz with
>> 40ms packet time? ****
>>
>> ** **
>>
>> ** **
>>
>> Thanks for any help,****
>>
>> ** **
>>
>> Dimosthenis****
>>
>> _________________________________________________________________________
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>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
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> _________________________________________________________________________
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> http://www.freeswitchsolutions.com
>
> 
> 
>
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>
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