gsm-codec-lib: doc/AMR-EFR-hybrid-emu annotate

annotate doc/AMR-EFR-hybrid-emu @ 585:3c6bf0d26ee7 default tip

TW-TS-005 reader: fix maximum line length bug TW-TS-005 section 4.1 states: The maximum allowed length of each line is 80 characters, not including the OS-specific newline encoding. The implementation of this line length limit in the TW-TS-005 hex file reader function in the present suite was wrong, such that lines of the full maximum length could not be read. Fix it. Note that this bug affects comment lines too, not just actual RTP payloads. Neither Annex A nor Annex B features an RTP payload format that goes to the maximum of 40 bytes, but if a comment line goes to the maximum allowed length of 80 characters not including the terminating newline, the bug will be triggered, necessitating the present fix.

author	Mychaela Falconia <falcon@freecalypso.org>
date	Tue, 25 Feb 2025 07:49:28 +0000
parents	ad032051166a
children

rev	line source
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	1 Emulation of other people's AMR-EFR hybrid implementations
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	2 ==========================================================
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	3
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	4 [Please see AMR-EFR-philosophy article for background information on the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	5 differences between classic GSM-EFR and the 12k2 mode of AMR, and how ETSI/3GPP
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	6 loosened their regulation on bit-exactness of EFR, then continue here.]
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	7
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	8 Experiments reveal that the extant commercial GSM networks of T-Mobile USA and
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	9 Telcel Mexico (and likely other countries' GSM networks too) use a GSM speech
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	10 transcoder implementation that performs EFR encoding and decoding (for times
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	11 when the MS declares no support for AMR and the network falls back to EFR) per
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	12 the alternative which we call AMR-EFR hybrid. The needed experiments are done
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	13 by using a FreeCalypso phone or devboard as the MS (declaring yourself to the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	14 network as non-AMR-capable via AT%SPVER), capturing TCH DL and feeding TCH UL
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	15 with FreeCalypso tools, and using a SIP-to-PSTN connectivity provider (BulkVS
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	16 or Anveo) on the other end of the test call that allows the experimenter to
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	17 receive the PCMU or PCMA sample stream coming out of the GSM network's speech
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	18 transcoder and feed a crafted PCMU/PCMA sample stream in the other direction.
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	19
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	20 In this experimental setup, bit-exact details of how the GSM network under study
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	21 implements EFR decoding can be tested by feeding a controlled sequence of EFR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	22 codec frames (beginning with at least two DHFs) to GSM Um uplink and observing
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	23 the PCMU or PCMA sample stream received on the IP-PSTN end of the call.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	24 Similarly, bit-exact details of how the NUS implements EFR encoding can be
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	25 tested by feeding controlled PCMU/PCMA sample streams into the call from IP-PSTN
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	26 and observing what the network emits on GSM Um downlink. In the latter case,
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	27 frame synchronization finding tricks described in ETSI/3GPP test sequence specs
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	28 need to included as part of the experiment.
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	29
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	30 When these experiments were performed on the GSM networks of T-Mobile USA and
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	31 Telcel Mexico, it was immediately apparent that they do not implement EFR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	32 following the original bit-exact code of GSM 06.53: feeding any of the original
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	33 EFR test sequences from GSM 06.54 to the NUS does not produce matching results.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	34 However, when I tried feeding EFR codec frame sequences from amr122_efr.zip
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	35 (the late addendum to GSM 06.54 for the AMR-EFR hybrid option) to GSM UL, the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	36 PCMU (T-Mobile USA) or PCMA (Telcel Mexico) output from the GSM network's EFR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	37 decoder matched _those_ test sequences, indicating that these networks use the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	38 AMR-EFR alternative implementation.
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	39
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	40 Creating tinkerer-oriented FOSS tools that can emulate or replicate the poorly
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	41 defined "EFR alternative 2" implemented by these extant commercial networks has
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	42 been a sportive challenge ever since. The present development in Themyscira
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	43 GSM codec libraries and utilities suite is a step toward conquering that
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	44 challenge: we are now able to replicate the mystery commercial transcoder in
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	45 non-DTX operation, specifically:
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	46
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	47 a) We can feed a SID-free stream of EFR codec frames to GSM UL, beginning with
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	48 DHF, and get the expected result on PCMU or PCMA;
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	49
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	50 b) In the encoder direction, for the first 7 frames after EHF, before DTX is
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	51 allowed to kick in, we can get GSM DL output from the network that matches
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	52 our expectations.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	53
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	54 Encoder 5 ms delay and DHF transformation
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	55 =========================================
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	56
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	57 One of the diffs between classic EFR and MR122 in the encoder direction is the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	58 artificial delay of 5 ms introduced in the AMR version. In true multirate
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	59 operation this delay is needed to support seamless switching between codec
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	60 modes, but when the only allowed codec rate is 12k2 (which is the case with EFR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	61 by definition), this delay is pure waste. (Needless to say, an extra delay of
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	62 5 ms is nothing compared to the egregious latencies introduced by today's ugly
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	63 and horrible world of IP-based transport everywhere, but still...) This
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	64 artificial 5 ms delay in the encoder is the reason for the DHF difference
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	65 between EFR and MR122 - but here is the wild part: instead of recognizing this
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	66 artificial delay as unnecessary and wasteful for 12k2-only EFR and removing it
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	67 from the AMR-EFR hybrid contraption, those commercial transcoder vendors and
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	68 the people who prepared amr122_efr.zip for ETSI/3GPP (were they the same
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	69 people?) kept this 5 ms encoder delay, keeping the whole encoder unchanged AMR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	70 except for whatever insane trickery they did to fit EFR DTX logic and EFR SID
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	71 generation into it, but added special DHF transformation logic on the output of
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	72 this AMR encoder to produce compliant EFR DHF when the input is EHF.
136 8eb0e7a39409 doc: document command line utilities Mychaela Falconia <falcon@freecalypso.org> parents: diff changeset	73
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	74 Exactly how this DHF transformation is done in those actually-deployed AMR-EFR
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	75 hybrid encoders is a bit of a mystery. My first thought was to compare the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	76 speech parameters emitted by the AMR encoder against MR122 DHF, and if the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	77 result is a match, replace that MR122-DHF parameter set with EFR DHF. This
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	78 approach is implemented in the simple amr_dhf_subst_efr() function in libtwamr.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	79 One distinctive signature of this approach is that the output of a hybrid
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	80 encoder following this method can never equal MR122 DHF: this one particular
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	81 bit pattern is precluded from the set of possible outputs under all conditions.
457 9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	82
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	83 However, subsequent experiments quickly revealed that the logic implemented by
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	84 the transcoder in the network of T-Mobile USA must be different. One of the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	85 counter-intuitive effects of the 5 ms artificial delay in the MR122 encoder is
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	86 what happens when the encoder is in its homed state and you feed it an input
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	87 frame whose first 120 samples are all 0x0008, but some (as few as one or as many
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	88 as all) of the last 40 samples are different. This frame does not meet the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	89 definition of EHF and won't be recognized as such - the encoder won't get
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	90 rehomed once again after processing this frame - yet the output will be
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	91 bit-exact MR122 DHF. How do those AMR-EFR hybrid encoders handle this case?
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	92
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	93 Experiments on T-Mobile reveal that in the case in question, the encoded frame
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	94 is emitted with the bit pattern of MR122 DHF, not transformed into EFR DHF.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	95 Because MR122-DHF output is impossible with an encoder that implements logic
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	96 like our amr_dhf_subst_efr() first cut, we know (by modus tollens) that
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	97 T-Mobile's implementation uses some different logic.
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	98
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	99 Our new (current) working model is implemented in amr_dhf_subst_efr2(): we
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	100 replace the output of the AMR encoder with EFR DHF if the raw encoder output
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	101 was MR122 DHF and the input frame was EHF. This version appears to match
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	102 the observed behavior of T-Mobile USA so far.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	103
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	104 EFR DHF in the decoder direction
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	105 ================================
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	106
467 ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	107 The way decoder homing works in all ETSI/3GPP-defined speech codecs, there is
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	108 an explicit check against known DHF bit pattern (up to first subframe only) at
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	109 the beginning of the decoder (if the decoder is homed and the input is DHF per
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	110 this reduced check, artificially emit EHF, stay homed and do nothing more), and
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	111 a second similar check against the known DHF bit pattern (full frame comparison
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	112 this time) at the end of the decoder, triggering the state reset function on
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	113 match. These checks are (and can only be) implemented by explicit comparison
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	114 against a known hard-coded DHF pattern - hence it doesn't matter in the decoder
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	115 case whether the DHF is natural (as in all properly ETSI-defined codecs) or
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	116 artificial as in AMR-EFR hybrid. Thus the "correct" handling of DHF in the
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	117 AMR-EFR hybrid decoder is a matter of replacing the check against MR122 DHF bit
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	118 pattern with a check against the different bit pattern of EFR DHF.
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	119
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	120 The decoder engine in libtwamr supports this different-DHF option for MR122
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	121 decoding by way of a bit set in the mode field in struct amr_param_frame - see
ad032051166a doc: AMR-EFR-hybrid-emu new article Mychaela Falconia <falcon@freecalypso.org> parents: 457 diff changeset	122 the detailed description in AMR-library-API article.
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	123
457 9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	124 Command line utilities for AMR-EFR hybrid
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	125 =========================================
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	126
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	127 The present package includes a small set of command line utilities that work
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	128 with the AMR-EFR hybrid described above:
311 83408f67a96c doc/AMR-EFR-philosophy: new article Mychaela Falconia <falcon@freecalypso.org> parents: 136 diff changeset	129
457 9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	130 amrefr-encode-r
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	131 amrefr-decode-r
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	132
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	133 These two utilities function just like gsmefr-encode-r and
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	134 gsmefr-decode-r described in Codec-utils article, but implement the
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	135 AMR-EFR hybrid version of the codec instead of original EFR. The
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	136 no-DTX limitation applies: amrefr-encode-r lacks -d option, and the
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	137 input to amrefr-decode-r must not contain any SID frames.
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	138
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	139 amrefr-tseq-enc
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	140 amrefr-tseq-dec
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	141
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	142 These two utilities are AMR-EFR counterparts to gsmefr-etsi-enc and
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	143 gsmefr-etsi-dec test programs described in EFR-testing article. They
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	144 pass all tests on the non-DTX t??_efr.* sequences in ETSI's
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	145 amr122_efr.zip, but not on any of the DTX sequences included in the
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	146 same ZIP. Just like amrefr-encode-r, amrefr-tseq-enc lacks -d option,
9bcf65088006 doc/AMR-EFR-philosophy: document implemented solution Mychaela Falconia <falcon@freecalypso.org> parents: 311 diff changeset	147 and amrefr-tseq-dec rejects input containing SID frames.

FreeCalypso > hg > gsm-codec-lib

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