Wireshark · Wireshark-users: [Wireshark-users] Some questions about dissecting EVS protocol

[Nan Xiao <xiaonan830818@xxxxxxxxx>]

Hi Community,

Greetings from me!

Now I am reading EVS dissection code, and have two questions:

(1) There is evs_132_bwctrf_idx_vals variable (https://gitlab.com/wireshark/wireshark/-/blob/master/epan/dissectors/packet-evs.c#L352) which helps to decode BW, CT and RF parameters. But from spec (https://www.etsi.org/deliver/etsi_ts/126400_126499/126445/12.01.00_60/ts_126445v120100p.pdf), 7.1.2 Bit allocation at 13.2 kbps section, I can only find following words:

> Note that the BW, CT, and RF parameters are combined together to form a single index. ......

But the spec doesn't say how to decode the "single index", so I just want to know where to find the definition of this index.

(2) From A.2.2.1.2 ToC byte section:
> F (1 bit): If set to 1, indicates that the corresponding frame is followed by another speech frame in this payload, implying that another ToC byte follows this entry; if set to 0, indicates that this frame is the last frame in this payload and no further header entry follows this entry.

I know there can be multiple TOCs followed by "speech data '', and use "F bit" in ToC byte to indicate whether this is the last TOC byte. I am just wondering if there is a possibility that the first byte of speech data can also have the "F bit" set to 1, so it is misunderstood as Toc byte?

Hope someone can give me some advice! Thanks very much in advance!

Best Regards

Nan Xiao