Gapk » History » Version 7
fixeria, 07/16/2018 04:09 PM
1 | 5 | fixeria | h1. GAPK (GSM Audio Pocket Knife) |
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2 | 1 | laforge | |
3 | 4 | fixeria | {{>toc}} |
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5 | The GAPK (GSM Audio Pocket Knife) is a project, the product of which is a core library (libosmogapk) and a command-line tool (osmo-gapk) for conversions between the various GSM related codecs (HR/FR/EFR/AMR) and PCM audio. It supports many different formats for the codec frames, including ETSI and IETF standardized formats, as well as vendor-specific formats like those found in the TI Calypso DSP (see [[OsmocomBB:]]) and those of Racal 6103/6113 GSM test equipment. |
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6 | 1 | laforge | |
7 | h2. Supported Codecs |
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8 | |||
9 | 6 | fixeria | |_.Codec|_.Description|_.Implementation| |
10 | |pcm|Raw PCM signed 16bits samples|native| |
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11 | 7 | fixeria | |hr|GSM 06.20 Half Rate codec|libgsmhr[1] (GSM 06.06 reference code)| |
12 | 6 | fixeria | |fr|GSM 06.10 Full Rate codec (classic gsm codec)|libgsm| |
13 | |efr|GSM 06.60 Enhanced Full Rate codec|opencore-amr| |
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14 | 1 | laforge | |amr|GSM 26.061 Adaptive Multi Rate codec|opencore-amr| |
15 | 7 | fixeria | |
16 | [1] Note: due to the licensing problems, the GSM 06.06 reference *code is not included* as a part of GAPK. Moreover, the reference implementation has a lot of problems, such as relatively low performance and poor code quality (lots of warnings, global state variables). |
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17 | 1 | laforge | |
18 | h2. Supported Formats |
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19 | |||
20 | |_.Format|_.Description| |
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21 | |amr-efr |Classic .amr file containing EFR (=AMR 12.2k) data| |
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22 | |gsm |Classic .gsm file format (and RTP payload for FR according to RFC3551)| |
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23 | |hr-ref-dec |3GPP HR Reference decoder code parameters file format| |
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24 | |hr-ref-enc |3GPP HR Reference encoder code parameters file format| |
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25 | |racal-hr |Racal HR TCH/H recording| |
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26 | |racal-fr |Racal FR TCH/F recording| |
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27 | |racal-efr |Racal EFR TCH/F recording| |
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28 | |rawpcm-s16le |Raw PCM samples Signed 16 bits little endian| |
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29 | |ti-hr |Texas Instrument HR TCH/H buffer format| |
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30 | |ti-fr |Texas Instrument FR TCH/F buffer format| |
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31 | |ti-efr |Texas Instrument EFR TCH/F buffer format| |
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32 | |amr-opencore |Input format to libopencore-amrnb| |
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33 | |rtp-amr |RTP payload for AMR according to RFC4867| |
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34 | |rtp-efr |RTP payload for EFR according to RFC3551| |
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35 | |rtp-hr-etsi |RTP payload for HR according to ETSI TS 101 318| |
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36 | |rtp-hr-ietf |RTP payload for HR according to IETF RFC5993| |
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37 | |||
38 | h2. Common use cases |
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39 | |||
40 | h3. RTP sink with audio playback on sound card |
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41 | |||
42 | You can run @gapk@ as a _RTP sink_, i.e. listening to a given UDP port for incoming RTP frames, decoding them from their respective audio codec and then playing them back via your computers' sound card. |
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43 | |||
44 | <pre> |
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45 | $ gapk -I 0.0.0.0/30000 -f rtp-amr -A default -g rawpcm-s16le |
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46 | </pre> |
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47 | |||
48 | where |
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49 | * *@-I 0.0.0.0/30000@* indicates the IP adddress (any) and UDP port (30000) to bind to and receive RTP frames on |
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50 | * *@-f rtp-amr@* indicates the codec. Use *@gsm, rtp-efr, rtp-amr, rtp-hr-etsi or rtp-hr-ietf@* depending on your use case |
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51 | * *@-A default@* is the alsa hardware device name (default is the default sound card) |
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52 | 2 | laforge | |
53 | h2. Source Code |
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55 | You can find the source code in git: |
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56 | * http://git.osmocom.org/gapk/ (cgit web interface) |
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57 | * @git clone git://git.osmocom.org/gapk@ for cloning the repository |
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58 | |||
59 | 3 | laforge | h2. Contact / Mailing List |
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61 | The project is too small to have it's own mailing list. Instead, we use the openbsc@lists.osmocom.org mailing list ("subscribe":http://lists.osmocom.org/mailman/listinfo/OpenBSC). Please observe the [[cellular-infrastructure:Mailing_List_Rules]]. |
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63 | 2 | laforge | h2. Authors |
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65 | @gapk@ as written by Sylvain Munaut with contributions from Harald Welte. |
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66 | |||
67 | It uses external libraries for the actual audio codecs, such as @libgsm@, @libopencore-amrnb@ nd the ETSI reference implementation for GSM-HR. |