Wireshark-dev: Re: [Wireshark-dev] RTP-MIDI strange field masks?

From: Evan Huus <eapache@xxxxxxxxx>
Date: Thu, 8 Jul 2021 14:32:14 -0400
Based on the 0xxxxxxx of your example and references like [1], I believe the masks are correct. MIDI seems to mostly use seven bit bytes schmucked together for some reason, so ignoring the high bit of each byte seems correct to me.

Evan

[1] http://midi.teragonaudio.com/tech/midispec/wheel.htm

On Thu, Jul 8, 2021 at 13:58 Martin Mathieson via Wireshark-dev <wireshark-dev@xxxxxxxxxxxxx> wrote:
These mask fields (0x7f7f, 0x7f7f7f7f, etc) look wrong to me, but I am worried I might be missing something?
Looking at an example in RFC 4695 (Song Position Pointer) I think this (on page 157) is saying that is it just a 2-byte field (and should therefore have a non-mask of 0x0)?

| Song Position Pointer          | 11110010 0xxxxxxx 0yyyyyyy |

These warnings are from ./tools/check_typed_item_calls.py --mask


Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.deltatime_2  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.deltatime_3  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.deltatime_4  - mask with non-contiguous bits 0x7f7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.pitch_bend  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sj_chapter_x_first_2  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sj_chapter_x_first_3  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sj_chapter_x_first_4  - mask with non-contiguous bits 0x7f7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.song_position_pointer  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_general_information_device_family  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_general_information_device_family_member  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_general_information_software_revision  - mask with non-contiguous bits 0x7f7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_sample_number  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_sample_period  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_sample_length  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_loop_start  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_loop_end  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_sample_dump_lp_trans_ln  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_non_realtime_fd_length  - mask with non-contiguous bits 0x7f7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_tune_freq  - mask with non-contiguous bits 0x7f7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_rt_ni_barnum  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_rt_dc_volume  - mask with non-contiguous bits 0x7f7f
Warning:  epan/dissectors/packet-rtp-midi.c filter= rtpmidi.sysex_common_rt_dc_balance  - mask with non-contiguous bits 0x7f7f
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