Add video streaming mode to TinyPilot logs (#1666)

Resolves #1490

Video demo:


https://github.com/tiny-pilot/tinypilot/assets/6730025/0165c85d-f9fa-4389-b98d-44de90843f5a

### Notes

1. When there are active WebRTC consumers, I see this in the Janus logs:
    ```
Oct 30 15:27:57 tinypilot janus[1790]: Creating new session:
3545622190134115; 0xed914e28
Oct 30 15:27:57 tinypilot janus[1790]: Creating new handle in session
3545622190134115: 8464226001965214; 0xed914e28 0xefb019c8
Oct 30 15:27:57 tinypilot janus[1790]: == ustreamer/main -- Creating
session 0xefb01650 ...
Oct 30 15:27:57 tinypilot janus[1790]: == ustreamer/video -- Memsink
opened; reading frames ...
Oct 30 15:27:57 tinypilot janus[1790]: [8464226001965214] Creating ICE
agent (ICE Full mode, controlling)
Oct 30 15:27:57 tinypilot janus[1790]: == ustreamer/audio -- Detected
host audio
Oct 30 15:27:57 tinypilot janus[1790]: == ustreamer/audio -- Pipeline
configured on 48000Hz; capturing ...
Oct 30 15:27:58 tinypilot janus[1790]: [8464226001965214] The DTLS
handshake has been completed
    ```
    
When there are no active WebRTC consumers, I see this in the Janus logs:
    ```
Oct 30 15:30:15 tinypilot janus[1790]: [WSS-0xed9005f8] Destroying
WebSocket client
Oct 30 15:30:15 tinypilot janus[1790]: Destroying session
3545622190134115; 0xed914e28
Oct 30 15:30:15 tinypilot janus[1790]: Detaching handle from ustreamer;
0xefb019c8 0xefb01650 0xefb019c8 (nil)
Oct 30 15:30:15 tinypilot janus[1790]: [8464226001965214] WebRTC
resources freed; 0xefb019c8 0xed914e28
Oct 30 15:30:15 tinypilot janus[1790]: == ustreamer/main -- Removing
session 0xefb01650 ...
Oct 30 15:30:15 tinypilot janus[1790]: == ustreamer/audio -- Pipeline
closed
Oct 30 15:30:15 tinypilot janus[1790]: == ustreamer/video -- Memsink
closed
Oct 30 15:30:16 tinypilot janus[1790]: == ustreamer/video -- No active
watchers, memsink disconnected
    ```
    
So based on the above log examples, [H264 mode is
active](https://github.com/tiny-pilot/tinypilot/blob/dda4d8b161eaac91db7f05a4e6bc14510b99f415/debian-pkg/opt/tinypilot-privileged/scripts/collect-debug-logs#L171-L173)
when the last Janus log that contains `ustreamer/video`, also contains
`Memsink opened; reading frames`. For example:

    ```
Oct 30 15:27:57 tinypilot janus[1790]: == ustreamer/video -- Memsink
opened; reading frames ...
    ```
    
    Otherwise, it is assumed that MJPEG is active.

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Author: jdeanwallace

app/cli.py

@@ -0,0 +1,20 @@
+from flask import Blueprint
+
+import db.settings
+
+# For invoking the commands on the CLI you need to specify the FLASK_APP env
+# variable containing the path to the main file. E.g.: FLASK_APP=app/main.py
+cli_blueprint = Blueprint('cli', __name__)
+
+
+@cli_blueprint.cli.command('streaming-mode')
+def streaming_mode():
+    """Prints TinyPilot's preferred video streaming mode, either H264 or MJPEG.
+
+    Note: this doesn't represent the currently active video streaming mode
+    because H264 can fail and fall back to MJPEG.
+
+    Example of invocation:
+        flask cli streaming-mode
+    """
+    print(db.settings.Settings().get_streaming_mode().value)

app/main.py

@@ -11,6 +11,7 @@
 # app-wide logger class before any other module loads it.
 import log
 import api
+import cli
 import json_response
 import license_notice
 import secret_key
@@ -49,6 +50,7 @@
 app.register_blueprint(api.api_blueprint)
 app.register_blueprint(license_notice.blueprint)
 app.register_blueprint(views.views_blueprint)
+app.register_blueprint(cli.cli_blueprint)
 
 
 @app.errorhandler(flask_wtf.csrf.CSRFError)

debian-pkg/opt/tinypilot-privileged/scripts/collect-debug-logs

@@ -163,6 +163,23 @@ print_info "Checking for voltage issues..."
   printf "\n\n"
 } >> "${LOG_FILE}"
 
+print_info "Checking TinyPilot streaming mode..."
+{
+  echo "Streaming mode"
+  echo "Selected mode: $(/opt/tinypilot/scripts/streaming-mode)"
+  printf "Current mode: "
+  # H264 mode is considered active when the last Janus video log line contains
+  # "Memsink opened; reading frames".
+  # https://github.com/tiny-pilot/ustreamer/blob/89fd83bfc187ed592e9582be077fa1a005098532/janus/src/plugin.c#L148
+  if LAST_JANUS_VIDEO_LINE="$(journalctl --unit janus.service --quiet --reverse --lines 1 --grep 'ustreamer/video')" &&
+      [[ "${LAST_JANUS_VIDEO_LINE}" =~ 'Memsink opened; reading frames' ]]; then
+    printf "H264"
+  else
+    printf "MJPEG"
+  fi
+  printf "\n\n"
+} >> "${LOG_FILE}"
+
 print_info "Checking TinyPilot settings..."
 {
   printf "TinyPilot settings.yml\n"

scripts/streaming-mode

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Prints TinyPilot's preferred video streaming mode, either H264 or MJPEG.
+
+# Exit on first failure.
+set -e
+
+# Exit on unset variable.
+set -u
+
+SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
+readonly SCRIPT_DIR
+cd "${SCRIPT_DIR}/.."
+. ./venv/bin/activate
+
+# Create a dummy app settings file. The flask app needs a settings file to
+# start, but it's not necessary for this simple script, so we use a blank,
+# dummy version.
+APP_SETTINGS_FILE="$(mktemp)"
+readonly APP_SETTINGS_FILE
+export APP_SETTINGS_FILE
+
+export FLASK_APP='app/main.py'
+flask cli streaming-mode