Add Auto live view option with transcoding options (#24519)

* implement auto mode for single camera live view

* add transcoded live streams and stream ordering for auto mode

Cameras can now add lower quality live streams that go2rtc transcodes to H.264 on demand. `live.transcode` takes a source stream and a list of heights and bitrates, and each quality becomes a `{camera}_transcode_{height}p` stream. The config validator adds them to `live.streams` without moving any the user already placed, and drops them when transcoding is disabled or a height changes. `create_config.py` writes them into go2rtc's generated config at startup, and saving the config or deleting a camera syncs them through go2rtc's API, so no restart is needed. They use `#hardware`, so go2rtc picks a hardware encoder and falls back to the CPU when there isn't one.

The Live playback settings stream list can be reordered by drag, since its order is the auto ladder. Auto order sorts it by bitrate, measuring native streams through a new admin-only `/go2rtc/streams/{name}/bitrate` endpoint and using the configured bitrate for transcoded ones. A pure reorder wasn't saved before because RJSF, the settings form, and `update_yaml` all ignore map key order. Sections can now mark a map with `orderedMaps`, which sends the whole map with `replace_paths` so `config_set` rewrites it in order.

Transcoded streams aren't in `go2rtc.streams`, which only lists yaml streams, so the frontend treated them as not restreamed and fell back to jsmpeg. Every restream check now goes through `isRestreamedStream`.

Auto treated any stall with no bytes in the last 2 seconds as a dead camera and handed it to the error fallback, which went straight to jsmpeg. Heavy congestion can stop delivery completely, so congested viewers skipped every lower stream. Auto now declines only when stats show the camera offline, and a stall on a live camera steps down. The stream picker also has a Try highest quality button that sends auto back to the top stream.

* fixes

docs/docs/configuration/advanced/reference.md

@@ -901,6 +901,21 @@ live:
   streams:
     main_stream: main_stream_name
     sub_stream: sub_stream_name
+  # Optional: Lower-quality live streams transcoded by go2rtc while someone is watching.
+  # NOTE: Set at the camera level only.
+  transcode:
+    # Optional: Enable transcoded streams (default: shown below)
+    enabled: False
+    # Optional: go2rtc stream to transcode (default: the first live stream)
+    source: main_stream_name
+    # Optional: One transcoded stream per quality (default: shown below)
+    qualities:
+      - height: 720
+        bitrate: 1200
+      - height: 480
+        bitrate: 500
+      - height: 360
+        bitrate: 250
   # Optional: Set the height of the jsmpeg stream. (default: 720)
   # This must be less than or equal to the height of the detect stream. Lower resolutions
   # reduce bandwidth required for viewing the jsmpeg stream. Width is computed to match known aspect ratio.

docs/docs/configuration/live.md

@@ -92,7 +92,7 @@ go2rtc:
 
 ### Setting Streams For Live UI
 
-You can configure Frigate to allow manual selection of the stream you want to view in the Live UI. For example, you may want to view your camera's substream on mobile devices, but the full resolution stream on desktop devices. Setting the streams list will populate a dropdown in the UI's Live view that allows you to choose between the streams. This stream setting is _per device_ and is saved in your browser's local storage.
+You can configure Frigate to allow manual selection of the stream you want to view in the Live UI. For example, you may want to view your camera's substream on mobile devices, but the full resolution stream on desktop devices. Setting the streams list will populate a dropdown in the UI's Live view that allows you to choose between the streams. This stream setting is _per device_ and is saved in your browser's local storage. When a camera has more than one stream, the dropdown also offers **Auto**, which is used until you pick a specific stream. Auto starts on the first stream, steps down the list when your connection can't keep up, and steps back up when it recovers. To retry the top stream right away, select **Try highest quality** under the stream picker. List streams from highest to lowest quality, and avoid names that are plain numbers (such as `720`), which the browser sorts ahead of the others. In the UI, drag streams to reorder them, or use **Auto order** to sort them by measured bitrate.
 
 Additionally, when creating and editing camera groups in the UI, you can choose the stream you want to use for your camera group's Live dashboard.
 
@@ -158,6 +158,26 @@ cameras:
 </TabItem>
 </ConfigTabs>
 
+### Transcoded streams
+
+When a camera has no suitable sub stream, Frigate can add lower-quality streams that go2rtc transcodes to H.264 while someone is watching. They appear in the stream list like any other stream, so Auto mode can step down to them. Enable them under <NavPath path="Settings > Camera configuration > Live playback" />, or in YAML:
+
+```yaml
+cameras:
+  test_cam:
+    live:
+      transcode:
+        enabled: true
+        source: test_cam # optional, defaults to the first live stream
+        qualities:
+          - height: 720
+            bitrate: 1200 # kbps
+          - height: 480
+            bitrate: 500
+```
+
+Each quality becomes a go2rtc stream named `<camera>_transcode_<height>p`. go2rtc picks a hardware encoder automatically and falls back to the CPU, which costs CPU for each transcode while it is being watched. Check go2rtc's `api/ffmpeg/hardware` page to see which encoder it found. Using a sub stream as the `source` lowers the cost.
+
 ### WebRTC extra configuration:
 
 WebRTC works by creating a TCP or UDP connection on port `8555`. However, it requires additional configuration:
@@ -363,6 +383,13 @@ When your browser runs into problems playing back your camera streams, it will l
     - `Safari reported InvalidStateError.`
     - `Safari reported decoding errors.`
 
+- **mse-codec**
+  - What it means: go2rtc has no codec for this stream that the browser can play.
+  - What to try: Pick a stream with a codec the browser supports (H.264 is the most compatible), or use a browser that supports the stream's codec. In Auto, Frigate skips this stream for the rest of the session.
+
+  - Possible console messages from the player code:
+    - `mse: streams: codecs not matched: ...`
+
 - **stalled**
   - What it means: Playback has stalled because the player has fallen too far behind live (extended buffering or no data arriving).
   - What to try: This is usually indicative of the browser struggling to decode too many high-resolution streams at once. Try selecting a lower-bandwidth stream (substream), reduce the number of live streams open, improve the network connection, or lower the camera resolution. Also check your camera's keyframe (I-frame) interval: shorter intervals make playback start and recover faster. You can also try increasing the timeout value in <NavPath path="Settings > UI" /> .

docs/static/frigate-api.yaml

@@ -412,6 +412,39 @@ paths:
       security:
         - frigateAdminAuth: []
       x-required-role: admin
+  /go2rtc/streams/{stream_name}/bitrate:
+    get:
+      tags:
+        - Camera
+      summary: Go2Rtc Stream Bitrate
+      description: |-
+        **Access:** Admin role required.
+
+        Measure a go2rtc stream's bitrate over a few seconds.
+      operationId: 
+        go2rtc_stream_bitrate_go2rtc_streams__stream_name__bitrate_get
+      parameters:
+        - name: stream_name
+          in: path
+          required: true
+          schema:
+            type: string
+            title: Stream Name
+      responses:
+        '200':
+          description: Successful Response
+          content:
+            application/json:
+              schema: {}
+        '422':
+          description: Validation Error
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/HTTPValidationError'
+      security:
+        - frigateAdminAuth: []
+      x-required-role: admin
   /ffprobe:
     get:
       tags:
@@ -7731,6 +7764,11 @@ components:
           type: boolean
           title: Skip Save
           default: false
+        replace_paths:
+          items:
+            type: string
+          type: array
+          title: Replace Paths
       type: object
       title: AppConfigSetBody
     AppPostLoginBody: