[Membrane.RTP.Demuxer] Can't recognize in-band DTMF

[digiboridev]

Problem is simple, when DTMF rtp packets are sent demuxer just pass them through.
Its leads to error in opus parser because DTMF packets are not opus packets, or audio clicks with PCM* codecs.
Here is error from logs:

2025-12-04 14:34:48.228 [error] module=gen_server GenServer #PID<0.2187.0> terminating
** (RuntimeError) An error occured in parsing
(membrane_opus_plugin 0.20.6) lib/membrane_opus/parser.ex:185: Membrane.Opus.Parser.maybe_parse/5
(membrane_opus_plugin 0.20.6) lib/membrane_opus/parser.ex:103: Membrane.Opus.Parser.handle_buffer/4
(membrane_core 1.2.4) lib/membrane/core/callback_handler.ex:141: anonymous fn/3 in Membrane.Core.CallbackHandler.exec_callback/4
(membrane_core 1.2.4) lib/membrane/core/callback_handler.ex:144: Membrane.Core.CallbackHandler.exec_callback/4
(membrane_core 1.2.4) lib/membrane/core/callback_handler.ex:70: Membrane.Core.CallbackHandler.exec_and_handle_callback/5
(elixir 1.16.2) lib/enum.ex:2528: Enum."-reduce/3-lists^foldl/2-0-"/3
(membrane_core 1.2.4) lib/membrane/core/element/buffer_controller.ex:82: Membrane.Core.Element.BufferController.do_handle_incoming_buffers/4
(membrane_core 1.2.4) lib/membrane/core/element.ex:229: Membrane.Core.Element.handle_info/2
(stdlib 5.2.2) gen_server.erl:1095: :gen_server.try_handle_info/3
(stdlib 5.2.2) gen_server.erl:1183: :gen_server.handle_msg/6
(stdlib 5.2.2) proc_lib.erl:241: :proc_lib.init_p_do_apply/3

Last message: {Membrane.Core.Message, :buffer, [%Membrane.Buffer{payload: <<7, 138, 3, 192>>, pts: 5120000000, dts: nil, metadata: %{arrival_ts: 1764851688225074197, udp_source_address: {127, 0, 0, 1}, udp_source_port: 63862, rtp: %{timestamp: 286080, extensions: [], padding_size: 0, payload_type: 126, sequence_number: 302, ssrc: 3991512094, marker: true, total_header_size: 12, csrcs: []}}}], [for_pad: :input]}

2025-12-04 14:34:48.244 [error] module=Membrane.Core.ProcessHelper <0.2134.0>/ Terminating with reason: {:membrane_child_crash, {:opus_parser, 3991512094}, {%RuntimeError{message: "An error occured in parsing"}, [{Membrane.Opus.Parser, :maybe_parse, 5, [file: ~c"lib/membrane_opus/parser.ex", line: 185, error_info: %{module: Exception}]}, {Membrane.Opus.Parser, :handle_buffer, 4, [file: ~c"lib/membrane_opus/parser.ex", line: 103]}, {Membrane.Core.CallbackHandler, :"-exec_callback/4-fun-0-", 3, [file: ~c"lib/membrane/core/callback_handler.ex", line: 141]}, {Membrane.Core.CallbackHandler, :exec_callback, 4, [file: ~c"lib/membrane/core/callback_handler.ex", line: 144]}, {Membrane.Core.CallbackHandler, :exec_and_handle_callback, 5, [file: ~c"lib/membrane/core/callback_handler.ex", line: 70]}, {Enum, :"-reduce/3-lists^foldl/2-0-", 3, [file: ~c"lib/enum.ex", line: 2528]}, {Membrane.Core.Element.BufferController, :do_handle_incoming_buffers, 4, [file: ~c"lib/membrane/core/element/buffer_controller.ex", line: 82]}, {Membrane.Core.Element, :handle_info, 2, [file: ~c"lib/membrane/core/element.ex", line: 229]}, {:gen_server, :try_handle_info, 3, [file: ~c"gen_server.erl", line: 1095]}, {:gen_server, :handle_msg, 6, [file: ~c"gen_server.erl", line: 1183]}, {:proc_lib, :init_p_do_apply, 3, [file: ~c"proc_lib.erl", line: 241]}]}}

From the error you can see in last message that payload_type is 126 - it is DTMF rtp packet, but it forwarded to opus stream that sits on payload_type 111.

Pipeline where is happened

=======================
edit
It has the same SSRC, so it is probably in-band DTMF and needs to be distinguished using the SSRC-PT pair.

RTP metadata example:

2025-12-04 15:41:16.685 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 296640, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: <<218, 94, 78>>}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 32>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<255>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 321, marker: false, total_header_size: 28, csrcs: []}
2025-12-04 15:41:16.704 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 297600, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: <<218, 113, 186>>}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 33>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<255>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 322, marker: false, total_header_size: 28, csrcs: []}
2025-12-04 15:41:16.724 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 298560, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: "چI"}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 34>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<255>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 323, marker: false, total_header_size: 28, csrcs: []}
2025-12-04 15:41:16.743 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 299520, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: <<218, 154, 160>>}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 35>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<242>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 324, marker: false, total_header_size: 28, csrcs: []}
2025-12-04 15:41:16.763 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 300480, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: "ڮ^"}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 36>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<230>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 325, marker: false, total_header_size: 28, csrcs: []}
2025-12-04 15:41:16.804 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 301440, extensions: [], ssrc: 2805039703, payload_type: 126, padding_size: 0, sequence_number: 326, marker: true, total_header_size: 12, csrcs: []}
2025-12-04 15:41:16.804 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 301440, extensions: [], ssrc: 2805039703, payload_type: 126, padding_size: 0, sequence_number: 327, marker: true, total_header_size: 12, csrcs: []}
2025-12-04 15:41:16.804 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 301440, extensions: [], ssrc: 2805039703, payload_type: 126, padding_size: 0, sequence_number: 328, marker: true, total_header_size: 12, csrcs: []}
2025-12-04 15:41:16.825 [info] module=PrintRTPMetadata RTP Metadata: %{timestamp: 303360, extensions: [%Membrane.RTP.Header.Extension{identifier: 2, data: <<218, 238, 12>>}, %Membrane.RTP.Header.Extension{identifier: 3, data: <<1, 37>>}, %Membrane.RTP.Header.Extension{identifier: 1, data: <<255>>}], ssrc: 2805039703, payload_type: 111, padding_size: 0, sequence_number: 329, marker: false, total_header_size: 28, csrcs: []}