Media Server Configuration
This guide covers the configuration parameters for the Media Server, which handles MRCP communication between your voice platform and the speech services. For an overview of the Media Server architecture, see Media Server Connectivity.
Configuration File
Media Server settings are stored in media_server.conf, located at:
mrcp-api/docker/lumenvox/media_server.conf
To modify the configuration, follow these steps:
1. Extract the configuration from the running container:
docker cp docker-cloud-media-server-1:/etc/lumenvox ./lumenvox
2. Stop the running instance:
docker compose down
3. Configure volume mappings in docker-compose.yml:
Ensure your docker-compose.yml includes the following volume mappings so the container uses your local configuration:
- ./certs:/certs - ./lumenvox:/etc/lumenvox - ./logs:/var/log/lumenvox/
4. Edit the configuration file:
Modify ./lumenvox/media_server.conf with your desired settings.
5. Restart the service:
docker compose up -d
The MRCP-API instance will start with your updated configuration.
Global Settings
| Parameter | Default | Description |
mrcp_server_ip | 127.0.0.1 | IP address of the machine running the Media Server, used for RTSP/SIP responses. Must be reachable by your MRCP client platform. You must change this from the default. |
num_channels | 200 | Maximum concurrent channels/sessions. Valid range: 1–5000. |
mrcp_server_resmax | auto | Maximum concurrent resources. Should exceed your licensed port count. |
mrcp_server_port_base | 20000 | Lowest port used for MRCP. One port is used per MRCP resource. |
rtp_server_port_base | 25000 | Lowest port used for RTP/RTCP. One pair of ports is used per RTP resource. |
port_allocation_mode | 0 | Port allocation strategy. 0 = round-robin, 1 = first-available. |
listening_socket_size | 5 | Number of sockets allowed to backlog on the listen function. Valid range: 5–1000. |
max_num_rtp_packets_buffered | 0 | Unprocessed RTP packets held when not in recognition mode. Valid range: 0–1000. |
max_rtp_packet_size | 200 | Maximum size of received RTP packets in bytes. Valid range: 180–3000. |
Threading
Thread pool sizes default to auto, scaling automatically based on num_channels. Valid range for manual setting: 1–256.
| Parameter | Default | Description |
num_spawning_threads | auto | Threads for RTSP and SIP call creation. |
num_graveyard_threads | auto | Threads for RTSP and SIP session cleanup. |
num_mrcp_event_threads | auto | Threads for MRCP event processing. |
num_rtp_event_threads | auto | Threads for RTP event processing. |
SIP Configuration
| Parameter | Default | Description |
sip_port | 5060 | Port for MRCPv2 sessions via SIP. |
sips_port | 5061 | Port for MRCPv2 sessions via SIPS (secure SIP). |
sips_ssl_cert_file | self-signed | SSL certificate file (*.pem) for SIPS connections. |
sips_cipher_list | All valid | Allowed ciphers for SIPS SSL/TLS negotiation. |
sip_retransmission_interval | 0 | SIP retransmission interval in milliseconds (T1 timer). Valid: 0, or 500–32000. |
reuse_sip_tcp_socket | false | When true, keeps the SIP socket open even when all sessions are idle. |
RTSP Configuration
| Parameter | Default | Description |
rtsp_port | 554 | Port for incoming RTSP requests (MRCPv1). |
Maintenance Mode
| Parameter | Default | Description |
out_of_service | 0 | When enabled (1), rejects new sessions while existing sessions complete gracefully. |
rtsp_out_of_service_code | 404 | Response code for out-of-service RTSP clients. Valid: 404 or 503. |
sip_out_of_service_code | 503 | Response code for out-of-service SIP clients. Valid: 480, 486, 488, or 503. |
Vendor Specific Settings
| Parameter | Default | Description |
wind_back_time | 480 | Milliseconds of audio captured before voice activity detection, sent to ASR. Prevents clipping. Valid range: 0–5000. |
barge_in_timeout | 15000 | Milliseconds ASR waits for speech before returning a no-input event. Valid range: 0–40000. |
end_of_speech_timeout | 20000 | Milliseconds between barge-in and end-of-speech before timing out. Valid range: 0–400000. |
vad_stream_init_delay | 100 | Milliseconds of silence/noise guaranteed before user starts speaking. |
vad_bargein_threshold | 50 | VAD confidence threshold for triggering barge-in. Valid range: 0–100. |
compatibility_mode | 0 | Result encoding mode. 0 = standard, 1 = compatibility with other vendors. |
secure_context | 0 | When enabled (1), suppresses sensitive ASR data from logs. |
tts_secure_context | 1 | When enabled (1), suppresses sensitive TTS data from logs, replacing content with _SUPPRESSED. |
MRCP Settings
| Parameter | Default | Description |
save_waveform | false | Overrides the default behavior of the Save-Waveform header. |
waveform_url_location | (blank) | Disk location for saving waveforms. |
remove_waveform_files | (blank) | When enabled, waveform files are deleted at the end of each MRCP session. |
waveform_url_prefix | (blank) | Prefix for returned waveform URLs. |
send_sip_trying | 0 | When enabled (1), sends optional "100 TRYING" responses to INVITE requests. |
use_speech_incomplete | 0 | When enabled (1), uses the greater of speech-complete-timeout or speech-incomplete-timeout. |
MRCPv1 Settings
| Parameter | Default | Description |
recognizer_resource_url | /media/speechrecognizer | URL path for MRCPv1 speech recognition resource requests. |
synthesizer_resource_url | /media/synthesizer | URL path for MRCPv1 TTS resource requests. |
force_increment_rtsp_cseq | 0 | When enabled (1), increments RTSP CSeq numbers for server-originated packets. |
enable_rtsp_idle_timeout | 0 | When enabled (1), drops RTSP connections idle for more than 10 seconds. |
MRCPv2 Settings
| Parameter | Default | Description |
mrcp_tls_cert_file | self-signed | SSL certificate file (*.pem) for MRCPv2/TLS connections. |
mrcp_tls_cipher_list | All valid | Allowed ciphers for MRCPv2 TLS negotiation. |
allow_unauthenticated_srtp | 1 | When enabled (1), allows SIPS calls specifying UNAUTHENTICATED_SRTP in SDP crypto parameter. |
allow_unencrypted_srtp | 1 | When enabled (1), allows SIPS calls specifying UNENCRYPTED_SRTP in SDP crypto parameter. |