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author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Wed, 07 Jun 2023 23:52:31 +0000 |
parents | 1e9fe07f8f09 |
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The full Calypso hw+fw solution as delivered by TI (the relevant components here are the DSP, the official L1 code and RiViera Audio Service) implements an interesting feature called voice memos. The voice memo feature itself, plus FreeCalypso-added AT commands that exercise it, are described in the Voice-memo-feature article in our separate freecalypso-docs repository; the present document describes the available FC host tools utilities for working with these voice memo recordings. FreeCalypso tools for decoding voice memo files =============================================== If you have recorded a voice memo with AT@VMR and then read it out with fc-fsio, you can use additional FC tools to analyze it. The following tools are available, split between FC host tools and GSM codec libs & utilities packages: * fc-vm2gsmx (new with fc-host-tools-r18) takes a binary VM recording (as you would read out with fc-fsio) and converts it into extended-libgsm (gsmx) format defined in our GSM codec libraries & utilities package. This gsmx format is an extension of the classic libgsm (GSM 06.10) format, adding the possibility of SID frames and BFI markers (frame gaps) in addition to regular speech frames, thus it can represent the content of a voice memo recording made in DTX mode. These gsmx files can then be decoded into playable WAV with our gsmfr-decode utility. * fc-vm2hex (dates back to fc-host-tools-r5) converts a binary VM recording into ASCII hex format, similar to the old (2016) TCH DL recording format before it was extended in late 2022. Every fully-written frame is emitted in the hex output as 3 space-separated hex status words followed by a block of 66 hex digits giving the FR1 codec frame in the unchanged bit order of TI's DSP, and every skipped frame (one for which only status word 0 was written into the memo file) is emitted in the hex output as just that one word. The hex output from fc-vm2hex can be further fed to gsmfr-dlcap-parse utility (gsm-codec-lib package) for deeper analysis. FreeCalypso tools for external generation of voice memo files ============================================================= Using FreeCalypso tools, you can produce an external speech recording in GSM 06.10 FR1 codec format, convert it into TCS211 VM format, upload it into FC device FFS with fc-fsio, and then play these externally-produced voice memos with AT@VMP. The steps are as follows: 1) You can use gsmfr-encode to FR1-encode a speech sample from WAV into classic .gsm format, or gsmfr-encode-r if the source is raw BE instead of WAV. Alternatively, you can use any other off-the-shelf software that can encode FR1 and write libgsm format; SoX shipped with Slackware includes the necessary support. 2) fc-gsm2vm (unchanged since fc-host-tools-r5) converts a .gsm recording into non-DTX TCS211 VM format. At the present time we don't have any tools for producing external DTX-enabled VM recordings: the main limitation is that at least to this Mother's knowledge, the published source software community does not currently possess a GSM 06.10 encoding library that has been extended with VAD and DTX functions. There is classic libgsm from 1990s, used by everyone in the FOSS community who needs a GSM 06.10 encoder or decoder, but it doesn't do DTX; we (FreeCalypso and Themyscira Wireless) have produced our own libgsmfrp front-end that implements Rx DTX handler functions (that's how we can properly decode FR1 streams that contain SIDs and/or missing frames), but it doesn't help with DTX encoding. Therefore, our ability to produce TCS211-compatible VM recordings externally is currently limited to non-DTX mode.