[Freeswitch-users] Playback of AMR-WB files.

[Oancea, Dragos]

Hi
Mike, I did the PR, please see  FS-10642 .
<https://freeswitch.org/stash/plugins/servlet/jira-integration/issues/FS-10642>

Ivan, I think that trick would not work when trying to record when in BE
mode: https://tools.ietf.org/html/rfc4867#section-5 .
And yes, it will not work when the mode is changed during the call, but I
guess the mode change is uncommon, even if  AMR means actually "Adaptive
Multi-Rate" :) .

Cheers,
Dragos

On Wed, Aug 23, 2017 at 11:25 PM, Michael Jerris <mike at jerris.com> wrote:

> Thats a bug.  AMR-WB is not fixed rate so it should be setting that value
> to 0.  That change will make mod_native_file not load it.  Toss me a pull
> request to fix and I’ll merge it.
>
>
> On Aug 23, 2017, at 6:06 PM, ha.ppy.neko <ha.ppy.neko at gmail.com> wrote:
>
> Indeed. If mod_amrwb is compiled in paththrough mode it sets
> encoded_bytes_per_packet to 0 and mod_native_file skips this codec.
> But if mod_amrwb is compiled with transcoding support it sets
> encoded_bytes_per_packet to SWITCH_AMRWB_OUT_MAX_SIZE constant (61) and
> mod_native_file registers AMR-WB extension. That was the case for my
> installation.
>
> So my theory was that native playback fails because of incorrect packet
> size.
> According to module source AMR-WB has 9 bitrate modes with corresponding
> voice frame sizes (in bytes):
> 0 - 17
> 1 - 23
> 2 - 32
> 3 - 36
> 4 - 40
> 5 - 46
> 6 - 50
> 7 - 58
> 8 - 60
>
> I recorded test RAW file with FS and record application at max bitrate and
> resulting file was indeed stream of 62 bytes RTP payloads. 2 bytes AMR-WB
> header + 60 bytes of voice data.
> I recompiled mod_amrwb with encoded_bytes_per_packet set to 62 and was
> able to successfully play RAW file!
> There was warning "switch_core_file.c:358 File /tmp/recording.AMR-WB
> sample rate 8000 doesn't match requested rate 16000" but it sounded fine
> nevertheless.
>
> I think this will work with passthrough mode too (change
> encoded_bytes_per_packet param from 0 to 62), but I don't have time to test
> it yet.
>
> Of course I don't know if this change will not break other FS functions,
> any ideas?
>
> And second problem is that caller may request lower bitrate with frame
> size 40 for example and RAW file will be sliced incorrectly.
> Thats the real deal breaker. Any tips how to make native playback honor
> negotiated codec and set proper encoded_bytes_per_packet value?
>
>
> 2017-08-23 15:57 GMT+03:00 Michael Jerris <mike at jerris.com>:
>
>> That was actually fixed recently.  In current master code it won’t
>> register them.
>>
>> On Aug 22, 2017, at 6:50 PM, ha.ppy.neko <ha.ppy.neko at gmail.com> wrote:
>>
>> I am not sure, but it looks like for given mode AMR and AMR-WB files have
>> fixed frame size.
>> "The length of the speech frame is implicitly defined by the mode
>> indicated in the FT field":
>>
>> https://tools.ietf.org/html/rfc4867#page-35
>>
>> Anyway, it is strange that mod_native_file registers AMR and AMR-WB
>> formats if it could not support them.
>>
>> 2017-08-23 0:21 GMT+03:00 Anthony Minessale <anthony.minessale at gmail.com>
>> :
>>
>>> The question was answered by the log line you supplied.
>>>
>>> -- "cannot play or record native files with variable length data".
>>>
>>> VBR codecs are not a predictable size so you cannot make a raw file of
>>> it because you don't have any idea how big each packet is.
>>>
>>>
>
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