Fix stdout binary mode reset on Windows before streaming starts - #108
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droggen wants to merge 1 commit into
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Fix stdout binary mode reset on Windows before streaming starts#108droggen wants to merge 1 commit into
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Running rx_fm piped to sox or ffplay on Windows 11 leads to broken audio: crackling, no sound coming out. The issue is a text/binary mode problem in piping the output of rx_fm, where Windows resets the binary/text mode rather than preserving it. On Windows, suppress_stdout_stop() calls dup2() to restore the original stdout file descriptor after device enumeration/setup logging is redirected away. Windows' dup2() resets the destination descriptor to text mode as part of this restore, silently undoing the earlier _setmode(..., _O_BINARY) call made when output.file was set to stdout in main(). This caused every 0x0A byte in the raw audio/IQ sample stream written to stdout to be corrupted by CRLF translation when rx_fm/ rx_sdr output was piped to another process (e.g. sox, ffplay, direwolf) on Windows. Writing directly to a file was unaffected, since that code path does not go through suppress_stdout_stop(). Fix: re-apply _setmode(..., _O_BINARY) immediately after suppress_stdout_stop() in dongle_thread_fn, the last place stdout's mode is touched before the write loop begins. Verified by measuring 0x0D 0x0A byte-pair density in captured pipe output: ~0.7-1.3% before the fix vs ~0.002-0.005% baseline for clean random PCM data; ~0.004% after the fix, matching baseline.
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Running rx_fm piped to sox or ffplay on Windows 11 leads to broken audio: crackling, no sound coming out. The issue is a text/binary mode problem in piping the output of rx_fm, where Windows resets the binary/text mode rather than preserving it.
On Windows, suppress_stdout_stop() calls dup2() to restore the original stdout file descriptor after device enumeration/setup logging is redirected away. Windows' dup2() resets the destination descriptor to text mode as part of this restore, silently undoing the earlier _setmode(..., _O_BINARY) call made when output.file was set to stdout in main().
This caused every 0x0A byte in the raw audio/IQ sample stream written to stdout to be corrupted by CRLF translation when rx_fm/ rx_sdr output was piped to another process (e.g. sox, ffplay, direwolf) on Windows. Writing directly to a file was unaffected, since that code path does not go through suppress_stdout_stop().
Fix: re-apply _setmode(..., _O_BINARY) immediately after suppress_stdout_stop() in dongle_thread_fn, the last place stdout's mode is touched before the write loop begins.
Verified by measuring 0x0D 0x0A byte-pair density in captured pipe output: ~0.7-1.3% before the fix vs ~0.002-0.005% baseline for clean random PCM data; ~0.004% after the fix, matching baseline.