FreeCalypso > hg > gsm-codec-lib
annotate doc/PCM-file-formats @ 183:452c1d5a6268
libgsmefr BFI w/o data: emit zero output after decoder reset
In real-life usage, each EFR decoder session will most likely begin
with lots of BFI frames before the first real frame arrives. However,
because the spec-defined home state of the decoder is speech rather
than CN, our regular logic for BFI w/o data would have to feed
pseudorandom noise to the decoder (in the "fixed codebook excitation
pulses" part), which is silly to do at the beginning of the decoder
session right out of reset. Therefore, let's check reset_flag_old,
and if we are still in the reset state, simply emit zero output.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Tue, 03 Jan 2023 00:12:18 +0000 |
parents | a217a6eacbad |
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rev | line source |
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195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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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>
parents:
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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>
parents:
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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>
parents:
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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>
parents:
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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>
parents:
diff
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6 functions copied from opencore-amrnb test code. |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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7 |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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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>
parents:
diff
changeset
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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>
parents:
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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>
parents:
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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>
parents:
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12 of conversion utilities have been written: |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff
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13 |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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14 pcm16-raw2wav converts from raw format to WAV |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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15 pcm16-wav2raw converts from WAV to raw format |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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16 |
195911f2211c
document PCM format conversion utilities
Mychaela Falconia <falcon@freecalypso.org>
parents:
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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>
parents:
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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:
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19 |
a217a6eacbad
doc/PCM-file-formats: establish "robe" format
Mychaela Falconia <falcon@freecalypso.org>
parents:
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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:
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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>
parents:
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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>
parents:
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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
Mychaela Falconia <falcon@freecalypso.org>
parents:
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24 English pronunciation play on "raw BE", and it is also the ritual garment worn |
a217a6eacbad
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Mychaela Falconia <falcon@freecalypso.org>
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25 by Themyscira telecom priestesses. :-) |