falconia has submitted this change. ( https://gerrit.osmocom.org/c/libosmo-abis/+/43870?usp=email ) Change subject: cosmetic: update trau2rtp_gen documentation ...................................................................... cosmetic: update trau2rtp_gen documentation The testsuite for libosmo-abis includes a command line utility named trau2rtp_gen, documented in trau2rtp_gen.notes file. This utility is used for some unit tests, but it is also useful as a developer tool when working with E1-based BTS or in-band TFO. The documentation for trau2rtp_gen has got slightly out of date since it was written: * There is a new companion utility named trau2rtp_amr that exercises the separate libosmotrau API for AMR TRAU frames; * osmo_trau2rtp() for CSD modes has gained support for RTP output in TW-TS-007 format in addition to CLEARMODE; * The hex format emitted by trau2rtp_gen is defined in TW-TS-005, and there is now a newer version of that spec than the one previously linked. Update trau2rtp_gen.notes document for the current reality. Change-Id: I83f3964dd747932952d13f1e511f3d049d2a204f --- M tests/trau_conv/trau2rtp_gen.notes 1 file changed, 27 insertions(+), 22 deletions(-) Approvals: pespin: Looks good to me, approved Jenkins Builder: Verified fixeria: Looks good to me, but someone else must approve diff --git a/tests/trau_conv/trau2rtp_gen.notes b/tests/trau_conv/trau2rtp_gen.notes index 90027f5..b6b3617 100644 --- a/tests/trau_conv/trau2rtp_gen.notes +++ b/tests/trau_conv/trau2rtp_gen.notes @@ -57,7 +57,7 @@ but there are also tools that extract TRAU frames from E1 timeslot octet stream recordings and emit those extracted frames in the present hex format: -https://www.freecalypso.org/hg/gsm-net-reveng/file/tip/trau-decode +https://hg.themyscira.org/gsm-net-reveng/file/tip/trau-decode Example input for FRv1: @@ -84,7 +84,7 @@ codecs; trau2rtp_gen emits its generated RTP payloads in this hex format. Spec document: -https://www.freecalypso.org/specs/tw-ts-005-v010003.txt +https://www.themyscira.org/specs/tw-ts-005-v010100.txt What can one do with a TW-TS-005 hex file? Some possibilities: @@ -101,29 +101,34 @@ can be captured Abis-UL output from an E1 BTS, converted with trau2rtp_gen) into playable audio. -No AMR or CSD -============= +Separate utility for AMR +======================== -One limitation of the present trau2rtp_gen utility that should be noted is the -lack of support for AMR or CSD. The reasons for this limitation are: +The principal library API exercised by this trau2rtp_gen program, namely +osmo_trau2rtp(), does not support AMR - instead high-level decoding of AMR TRAU +frames requires use of the interworking facility of <osmocom/trau/amr_trau.h>. +At the level of command line utilities, a separate program exists that exercises +the AMR-specific TRAU to RTP conversion APIs - see tests/amr/trau2rtp_amr. -* AMR is currently not supported by osmo_trau2rtp() or osmo_rtp2trau() - functions, and it is not entirely clear if this API would be a good match for - the much more complex processing that will be needed in a software TRAU or - TRAU-emulating MGW for AMR. +No CSD support yet +================== -* CSD is supported by the chain of libosmotrau functions exercised by - trau2rtp_gen, but the resulting bloated RTP payloads cannot be represented in - TW-TS-005: spec section 4.1 limits each hex line to 80 characters, effectively - limiting the domain of application for this hex file format to RTP payloads - that are no larger than 40 bytes. +When the input is a TRAU frame in one of CSD modes, the output from +osmo_trau2rtp() can be either a 160-byte CLEARMODE payload or a much more +compact TW-TS-007 (compressed CSD) payload. The bloated CLEARMODE format cannot +be represented in TW-TS-005 hex files (it exceeds the line length limit imposed +by TW-TS-005 section 4.1), but the alternative TW-TS-007 compressed CSD format +_can_ be represented in TW-TS-005 hex - and the current version of TW-TS-005 +spec linked above includes Annex D that specifies such usage. -When and if a need arises to represent CSD frame streams in hex, there does not -seem to be one single solution that would be best for all use cases - instead -the problem might need to be approached on a case-by-case basis. For the -specific use case of unit tests, verifying correct operation of osmo_trau2rtp() -and osmo_rtp2trau() functions in data modes, one possible approach would be to +trau2rtp_gen utility can be extended to enable TW-TS-007 output and thereby add +support for at least one representation of GSM CSD in RTP - but no such +modification has been made yet. + +A need may also arise at some point to represent the bloated-but-standard +CLEARMODE formats in hex as well. TW-TS-005 cannot be used for that purpose, +but some other ad hoc hex format can be implemented quite easily - for example, copy what is currently done in raa_prime unit tests: break each 160-byte CSD RTP payload into 4 hex lines of 80 digits each. In any case, whichever hex format -is to be chosen for CSD, it will be its own separate test program, independent -of trau2rtp_gen. +is to be chosen for non-compressed CSD in CLEARMODE representation, it would +need to be its own separate test program, independent of trau2rtp_gen. -- To view, visit https://gerrit.osmocom.org/c/libosmo-abis/+/43870?usp=email To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings?usp=email Gerrit-MessageType: merged Gerrit-Project: libosmo-abis Gerrit-Branch: master Gerrit-Change-Id: I83f3964dd747932952d13f1e511f3d049d2a204f Gerrit-Change-Number: 43870 Gerrit-PatchSet: 1 Gerrit-Owner: falconia <falcon@freecalypso.org> Gerrit-Reviewer: Jenkins Builder Gerrit-Reviewer: falconia <falcon@freecalypso.org> Gerrit-Reviewer: fixeria <vyanitskiy@sysmocom.de> Gerrit-Reviewer: pespin <pespin@sysmocom.de>