FreeCalypso > hg > gsm-codec-lib
view doc/PCM-file-formats @ 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 | a217a6eacbad |
children |
line wrap: on
line source
What file format should be used for 16-bit PCM sample recordings? The first (in the order of development) group of utilities in the present package that need to read and write such files are gsm[e]fr-encode and gsm[e]fr-decode, designed to mirror amrnb-enc and amrnb-dec from opencore-amr FOSS package; these utilities read and write WAV files and even use WAV reading and writing functions copied from opencore-amrnb test code. However, as I (Mother Mychaela) keep developing more tools, my use cases become more diverse: in some use cases WAV is most convenient (e.g., when playing or recording with SoX tools), but in other use cases a raw sample file without any header is much more convenient. To address this diversity of use cases, a pair of conversion utilities have been written: pcm16-raw2wav converts from raw format to WAV pcm16-wav2raw converts from WAV to raw format Both utilities take a mandatory command line argument specifying the endian order for the raw format - there is no default. Going forward, I (Mother Mychaela) prefer big-endian format for raw PCM16 files: aside from it being the network byte order on the Internet, 16-bit and 32-bit numbers appear "naturally" in hex dumps in BE, but not in LE. Therefore, newly developed utilities will read and write PCM16 data in "robe" format - "robe" is English pronunciation play on "raw BE", and it is also the ritual garment worn by Themyscira telecom priestesses. :-)