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annotate doc/PCM-file-formats @ 194:f151d6c18b31

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libgsmefr/enc_lag6.c: perf opt
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 04 Jan 2023 03:36:39 +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
Mychaela Falconia <falcon@freecalypso.org>
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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
Mychaela Falconia <falcon@freecalypso.org>
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13
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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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
195911f2211c document PCM format conversion utilities
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16
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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17 Both utilities take a mandatory command line argument specifying the endian
195911f2211c document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
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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>
parents: 143
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19
a217a6eacbad doc/PCM-file-formats: establish "robe" format
Mychaela Falconia <falcon@freecalypso.org>
parents: 143
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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>
parents: 143
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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
Mychaela Falconia <falcon@freecalypso.org>
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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
Mychaela Falconia <falcon@freecalypso.org>
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23 developed utilities will read and write PCM16 data in "robe" format - "robe" is
a217a6eacbad doc/PCM-file-formats: establish "robe" format
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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. :-)