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annotate doc/PCM-file-formats @ 282:9ee8ad3d4d30

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frtest: rm gsmfr-hand-test and gsmfr-max-out utils These hack programs were never properly documented and were written only as part of a debug chase, in pursuit of a bug that ultimately turned out to be in our then-hacky patch to osmo-bts-sysmo, before beginning of proper patches in Osmocom. These hack programs need to be dropped from the present sw package because they depend on old libgsm, and we are eliminating that dependency.
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 14 Apr 2024 05:44:47 +0000
parents a217a6eacbad
children
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195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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1 What file format should be used for 16-bit PCM sample recordings? The first
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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2 (in the order of development) group of utilities in the present package that
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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3 need to read and write such files are gsm[e]fr-encode and gsm[e]fr-decode,
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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4 designed to mirror amrnb-enc and amrnb-dec from opencore-amr FOSS package;
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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5 these utilities read and write WAV files and even use WAV reading and writing
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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6 functions copied from opencore-amrnb test code.
195911f2211c document PCM format conversion utilities
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7
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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8 However, as I (Mother Mychaela) keep developing more tools, my use cases become
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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9 more diverse: in some use cases WAV is most convenient (e.g., when playing or
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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10 recording with SoX tools), but in other use cases a raw sample file without any
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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11 header is much more convenient. To address this diversity of use cases, a pair
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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12 of conversion utilities have been written:
195911f2211c document PCM format conversion utilities
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13
195911f2211c document PCM format conversion utilities
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14 pcm16-raw2wav converts from raw format to WAV
195911f2211c document PCM format conversion utilities
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15 pcm16-wav2raw converts from WAV to raw format
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16
195911f2211c document PCM format conversion utilities
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17 Both utilities take a mandatory command line argument specifying the endian
195911f2211c document PCM format conversion utilities
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18 order for the raw format - there is no default.
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a217a6eacbad doc/PCM-file-formats: establish "robe" format
Mychaela Falconia <falcon@freecalypso.org>
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19
a217a6eacbad doc/PCM-file-formats: establish "robe" format
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20 Going forward, I (Mother Mychaela) prefer big-endian format for raw PCM16 files:
a217a6eacbad doc/PCM-file-formats: establish "robe" format
Mychaela Falconia <falcon@freecalypso.org>
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21 aside from it being the network byte order on the Internet, 16-bit and 32-bit
a217a6eacbad doc/PCM-file-formats: establish "robe" format
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22 numbers appear "naturally" in hex dumps in BE, but not in LE. Therefore, newly
a217a6eacbad doc/PCM-file-formats: establish "robe" format
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23 developed utilities will read and write PCM16 data in "robe" format - "robe" is
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24 English pronunciation play on "raw BE", and it is also the ritual garment worn
a217a6eacbad doc/PCM-file-formats: establish "robe" format
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25 by Themyscira telecom priestesses. :-)