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

frigate/config/camera/live.py

@@ -1,8 +1,57 @@
-from pydantic import Field
+from pydantic import Field, field_validator
+
+from frigate.util.live_streams import DEFAULT_TRANSCODE_QUALITIES
 
 from ..base import FrigateBaseModel
 
-__all__ = ["CameraLiveConfig"]
+__all__ = ["CameraLiveConfig", "LiveTranscodeConfig", "LiveTranscodeQualityConfig"]
+
+
+class LiveTranscodeQualityConfig(FrigateBaseModel):
+    height: int = Field(
+        ge=144,
+        le=2160,
+        title="Height",
+        description="Output height in pixels; width follows the source aspect ratio.",
+    )
+    bitrate: int = Field(
+        ge=64,
+        title="Bitrate",
+        description="Target and maximum video bitrate in kbps.",
+    )
+
+
+class LiveTranscodeConfig(FrigateBaseModel):
+    enabled: bool = Field(
+        default=False,
+        title="Enable transcoded streams",
+        description="Add lower-quality live streams that go2rtc transcodes in real time while someone is watching.",
+    )
+    source: str | None = Field(
+        default=None,
+        title="Source stream",
+        description="go2rtc stream to transcode. Defaults to the first live stream.",
+    )
+    qualities: list[LiveTranscodeQualityConfig] = Field(
+        default_factory=lambda: [
+            LiveTranscodeQualityConfig(**quality)
+            for quality in DEFAULT_TRANSCODE_QUALITIES
+        ],
+        title="Qualities",
+        description="One transcoded stream is added per quality.",
+    )
+
+    @field_validator("qualities")
+    @classmethod
+    def validate_unique_heights(
+        cls, qualities: list[LiveTranscodeQualityConfig]
+    ) -> list[LiveTranscodeQualityConfig]:
+        heights = [quality.height for quality in qualities]
+
+        if len(heights) != len(set(heights)):
+            raise ValueError("Transcoded stream heights must be unique.")
+
+        return qualities
 
 
 class CameraLiveConfig(FrigateBaseModel):
@@ -11,6 +60,11 @@ class CameraLiveConfig(FrigateBaseModel):
         title="Live stream names",
         description="Mapping of configured stream names to restream/go2rtc names used for live playback.",
     )
+    transcode: LiveTranscodeConfig = Field(
+        default_factory=LiveTranscodeConfig,
+        title="Transcoded streams",
+        description="Lower-quality live streams transcoded on demand by go2rtc.",
+    )
     height: int = Field(
         default=720,
         title="Live height",