frigate/frigate/output/preview.py

"""Handle outputting low res / fps preview segments from decoded frames."""

import datetime
import logging
import os
import shutil
import subprocess as sp
import threading
import time
from pathlib import Path
from typing import Any

import cv2
import numpy as np

from frigate.comms.inter_process import InterProcessRequestor
from frigate.config import CameraConfig, RecordQualityEnum
from frigate.const import CACHE_DIR, CLIPS_DIR, INSERT_PREVIEW, PREVIEW_FRAME_TYPE
from frigate.ffmpeg_presets import (
    FPS_VFR_PARAM,
    EncodeTypeEnum,
    parse_preset_hardware_acceleration_encode,
)
from frigate.models import Previews
from frigate.util.image import copy_yuv_to_position, get_blank_yuv_frame, get_yuv_crop

logger = logging.getLogger(__name__)

FOLDER_PREVIEW_FRAMES = "preview_frames"
PREVIEW_CACHE_DIR = os.path.join(CACHE_DIR, FOLDER_PREVIEW_FRAMES)
PREVIEW_SEGMENT_DURATION = 3600  # one hour
# important to have lower keyframe to maintain scrubbing performance
PREVIEW_KEYFRAME_INTERVAL = 40
PREVIEW_HEIGHT = 180
PREVIEW_QUALITY_WEBP = {
    RecordQualityEnum.very_low: 70,
    RecordQualityEnum.low: 80,
    RecordQualityEnum.medium: 80,
    RecordQualityEnum.high: 80,
    RecordQualityEnum.very_high: 86,
}
PREVIEW_QUALITY_BIT_RATES = {
    RecordQualityEnum.very_low: 7168,
    RecordQualityEnum.low: 8196,
    RecordQualityEnum.medium: 9216,
    RecordQualityEnum.high: 9864,
    RecordQualityEnum.very_high: 10096,
}
# the -qmax param for ffmpeg prevents the encoder from overly compressing frames while still trying to hit the bitrate target
# lower values are higher quality. This is especially important for iniitial frames in the segment
PREVIEW_QMAX_PARAM = {
    RecordQualityEnum.very_low: "",
    RecordQualityEnum.low: "",
    RecordQualityEnum.medium: "",
    RecordQualityEnum.high: " -qmax 25",
    RecordQualityEnum.very_high: " -qmax 25",
}


def get_cache_image_name(camera: str, frame_time: float) -> str:
    """Get the image name in cache."""
    return os.path.join(
        CACHE_DIR,
        f"{FOLDER_PREVIEW_FRAMES}/preview_{camera}-{frame_time}.{PREVIEW_FRAME_TYPE}",
    )


def get_most_recent_preview_frame(
    camera: str, before: float | None = None
) -> str | None:
    """Get the most recent preview frame for a camera."""
    if not os.path.exists(PREVIEW_CACHE_DIR):
        return None

    try:
        # files are named preview_{camera}-{timestamp}.webp
        # we want the largest timestamp that is less than or equal to before
        preview_files = [
            f
            for f in os.listdir(PREVIEW_CACHE_DIR)
            if f.startswith(f"preview_{camera}-")
            and f.endswith(f".{PREVIEW_FRAME_TYPE}")
        ]

        if not preview_files:
            return None

        # sort by timestamp in descending order
        # filenames are like preview_front-1712345678.901234.webp
        preview_files.sort(reverse=True)

        if before is None:
            return os.path.join(PREVIEW_CACHE_DIR, preview_files[0])

        for file_name in preview_files:
            try:
                # Extract timestamp: preview_front-1712345678.901234.webp
                # Split by dash and extension
                timestamp_part = file_name.split("-")[-1].split(
                    f".{PREVIEW_FRAME_TYPE}"
                )[0]
                timestamp = float(timestamp_part)

                if timestamp <= before:
                    return os.path.join(PREVIEW_CACHE_DIR, file_name)
            except (ValueError, IndexError):
                continue

        return None
    except Exception as e:
        logger.error(f"Error searching for most recent preview frame: {e}")
        return None


class FFMpegConverter(threading.Thread):
    """Convert a list of still frames into a vfr mp4."""

    def __init__(
        self,
        config: CameraConfig,
        frame_times: list[float],
        requestor: InterProcessRequestor,
    ):
        super().__init__(name=f"{config.name}_preview_converter")
        self.config = config
        self.frame_times = frame_times
        self.requestor = requestor
        self.path = os.path.join(
            CLIPS_DIR,
            f"previews/{self.config.name}/{self.frame_times[0]}-{self.frame_times[-1]}.mp4",
        )

        # write a PREVIEW at fps and 1 key frame per clip
        self.ffmpeg_cmd = parse_preset_hardware_acceleration_encode(
            config.ffmpeg.ffmpeg_path,
            "default",
            input="-f concat -y -protocol_whitelist pipe,file -safe 0 -threads 1 -i /dev/stdin",
            output=f"-threads 1 -g {PREVIEW_KEYFRAME_INTERVAL} -bf 0 -b:v {PREVIEW_QUALITY_BIT_RATES[self.config.record.preview.quality]}{PREVIEW_QMAX_PARAM[self.config.record.preview.quality]} {FPS_VFR_PARAM} -movflags +faststart -pix_fmt yuv420p {self.path}",
            type=EncodeTypeEnum.preview,
        )

    def run(self) -> None:
        # generate input list
        item_count = len(self.frame_times)
        playlist = []

        for t_idx in range(0, item_count):
            if t_idx == item_count - 1:
                # last frame does not get a duration
                playlist.append(
                    f"file '{get_cache_image_name(self.config.name, self.frame_times[t_idx])}'"  # type: ignore[arg-type]
                )
                continue

            playlist.append(
                f"file '{get_cache_image_name(self.config.name, self.frame_times[t_idx])}'"  # type: ignore[arg-type]
            )
            playlist.append(
                f"duration {self.frame_times[t_idx + 1] - self.frame_times[t_idx]}"
            )

        Path(self.path).parent.mkdir(parents=True, exist_ok=True)

        try:
            p = sp.run(
                self.ffmpeg_cmd.split(" "),
                input="\n".join(playlist),
                encoding="ascii",
                capture_output=True,
            )
        except BlockingIOError:
            logger.warning(
                f"Failed to create preview for {self.config.name}, retrying..."
            )
            time.sleep(2)
            p = sp.run(
                self.ffmpeg_cmd.split(" "),
                input="\n".join(playlist),
                encoding="ascii",
                capture_output=True,
            )

        start = self.frame_times[0]
        end = self.frame_times[-1]

        if p.returncode == 0:
            logger.debug("successfully saved preview")
            self.requestor.send_data(
                INSERT_PREVIEW,
                {
                    Previews.id.name: f"{self.config.name}_{end}",
                    Previews.camera.name: self.config.name,
                    Previews.path.name: self.path,
                    Previews.start_time.name: start,
                    Previews.end_time.name: end,
                    Previews.duration.name: end - start,
                },
            )
        else:
            logger.error(f"Error saving preview for {self.config.name} :: {p.stderr}")

        # unlink files from cache
        # don't delete last frame as it will be used as first frame in next segment
        for t in self.frame_times[0:-1]:
            Path(get_cache_image_name(self.config.name, t)).unlink(missing_ok=True)  # type: ignore[arg-type]


class PreviewRecorder:
    def __init__(self, config: CameraConfig) -> None:
        self.config = config
        self.camera_name: str = config.name or ""
        self.start_time: float = 0
        self.last_output_time: float = 0
        self.offline = False
        self.output_frames: list[float] = []

        if config.detect.width is None or config.detect.height is None:
            raise ValueError("Detect width and height must be set for previews.")

        self.detect_width: int = config.detect.width
        self.detect_height: int = config.detect.height

        if self.detect_width > self.detect_height:
            self.out_height = PREVIEW_HEIGHT
            self.out_width = (
                int((self.detect_width / self.detect_height) * self.out_height) // 4 * 4
            )
        else:
            self.out_width = PREVIEW_HEIGHT
            self.out_height = (
                int((self.detect_height / self.detect_width) * self.out_width) // 4 * 4
            )

        # create communication for finished previews
        self.requestor = InterProcessRequestor()

        y, u1, u2, v1, v2 = get_yuv_crop(
            self.config.frame_shape_yuv,
            (
                0,
                0,
                self.config.frame_shape[1],
                self.config.frame_shape[0],
            ),
        )
        self.channel_dims = {
            "y": y,
            "u1": u1,
            "u2": u2,
            "v1": v1,
            "v2": v2,
        }

        # end segment at end of hour (use UTC to avoid DST issues)
        self.segment_end = (
            (datetime.datetime.now(datetime.UTC) + datetime.timedelta(hours=1))
            .replace(minute=0, second=0, microsecond=0)
            .timestamp()
        )

        Path(PREVIEW_CACHE_DIR).mkdir(exist_ok=True)
        Path(os.path.join(CLIPS_DIR, f"previews/{config.name}")).mkdir(
            parents=True, exist_ok=True
        )

        # check for existing items in cache
        start_ts = (
            datetime.datetime.now(datetime.UTC)
            .replace(minute=0, second=0, microsecond=0)
            .timestamp()
        )

        file_start = f"preview_{config.name}-"
        start_file = f"{file_start}{start_ts}.webp"

        for file in sorted(os.listdir(os.path.join(CACHE_DIR, FOLDER_PREVIEW_FRAMES))):
            if not file.startswith(file_start):
                continue

            if file < start_file:
                os.unlink(os.path.join(PREVIEW_CACHE_DIR, file))
                continue

            try:
                file_time = file.split("-")[-1][: -(len(PREVIEW_FRAME_TYPE) + 1)]

                if not file_time:
                    continue

                ts = float(file_time)
            except ValueError:
                continue

            if self.start_time == 0:
                self.start_time = ts

            self.last_output_time = ts
            self.output_frames.append(ts)

    def reset_frame_cache(self, frame_time: float) -> None:
        self.segment_end = (
            (
                datetime.datetime.fromtimestamp(frame_time, tz=datetime.UTC)
                + datetime.timedelta(hours=1)
            )
            .replace(minute=0, second=0, microsecond=0)
            .timestamp()
        )
        self.start_time = frame_time
        self.last_output_time = frame_time
        self.output_frames = []

    def should_write_frame(
        self,
        current_tracked_objects: list[dict[str, Any]],
        motion_boxes: list[list[int]],
        frame_time: float,
    ) -> bool:
        """Decide if this frame should be added to PREVIEW."""
        if not self.config.record.enabled:
            return False

        active_objs = get_active_objects(
            frame_time, self.config, current_tracked_objects
        )

        preview_output_fps = 2 if any(o["label"] == "car" for o in active_objs) else 1

        # limit output to 1 fps
        if (frame_time - self.last_output_time) < 1 / preview_output_fps:
            return False

        # send frame if a non-stationary object is in a zone
        if len(active_objs) > 0:
            self.last_output_time = frame_time
            return True

        if len(motion_boxes) > 0:
            self.last_output_time = frame_time
            return True

        # ensure that at least 2 frames are written every minute
        if frame_time - self.last_output_time > 30:
            self.last_output_time = frame_time
            return True

        return False

    def write_frame_to_cache(self, frame_time: float, frame: np.ndarray) -> None:
        # resize yuv frame
        small_frame: np.ndarray = np.zeros(
            (self.out_height * 3 // 2, self.out_width), np.uint8
        )
        copy_yuv_to_position(
            small_frame,
            (0, 0),
            (self.out_height, self.out_width),
            frame,
            self.channel_dims,
            cv2.INTER_AREA,
        )
        small_frame = cv2.cvtColor(
            small_frame,
            cv2.COLOR_YUV2BGR_I420,
        )
        cache_path = get_cache_image_name(self.camera_name, frame_time)

        if not cv2.imwrite(
            cache_path,
            small_frame,
            [
                int(cv2.IMWRITE_WEBP_QUALITY),
                PREVIEW_QUALITY_WEBP[self.config.record.preview.quality],
            ],
        ):
            logger.error("Failed to write preview frame to %s", cache_path)

    def write_data(
        self,
        current_tracked_objects: list[dict[str, Any]],
        motion_boxes: list[list[int]],
        frame_time: float,
        frame: np.ndarray,
    ) -> None:
        self.offline = False

        # always write the first frame
        if self.start_time == 0:
            self.start_time = frame_time
            self.output_frames.append(frame_time)
            self.write_frame_to_cache(frame_time, frame)
            return

        # check if PREVIEW clip should be generated and cached frames reset
        if frame_time >= self.segment_end:
            if len(self.output_frames) > 0:
                # save last frame to ensure consistent duration
                if self.config.record:
                    self.output_frames.append(frame_time)
                    self.write_frame_to_cache(frame_time, frame)

                # write the preview if any frames exist for this hour
                FFMpegConverter(
                    self.config,
                    self.output_frames,
                    self.requestor,
                ).start()
            else:
                logger.debug(
                    f"Not saving preview for {self.camera_name} because there are no saved frames."
                )

            self.reset_frame_cache(frame_time)

            # include first frame to ensure consistent duration
            if self.config.record.enabled:
                self.output_frames.append(frame_time)
                self.write_frame_to_cache(frame_time, frame)

            return
        elif self.should_write_frame(current_tracked_objects, motion_boxes, frame_time):
            self.output_frames.append(frame_time)
            self.write_frame_to_cache(frame_time, frame)
            return

    def flag_offline(self, frame_time: float) -> None:
        if not self.offline:
            self.write_frame_to_cache(
                frame_time,
                get_blank_yuv_frame(self.detect_width, self.detect_height),
            )
            self.offline = True

        # check if PREVIEW clip should be generated and cached frames reset
        if frame_time >= self.segment_end:
            if len(self.output_frames) == 0:
                # camera has been offline for entire hour
                # we have no preview to create
                self.reset_frame_cache(frame_time)
                return

            old_frame_path = get_cache_image_name(
                self.camera_name, self.output_frames[-1]
            )
            new_frame_path = get_cache_image_name(self.camera_name, frame_time)
            shutil.copy(old_frame_path, new_frame_path)

            # save last frame to ensure consistent duration
            self.output_frames.append(frame_time)
            FFMpegConverter(
                self.config,
                self.output_frames,
                self.requestor,
            ).start()

            self.reset_frame_cache(frame_time)

    def stop(self) -> None:
        self.requestor.stop()


def get_active_objects(
    frame_time: float, camera_config: CameraConfig, all_objects: list[dict[str, Any]]
) -> list[dict[str, Any]]:
    """get active objects for detection."""
    return [
        o
        for o in all_objects
        if o["motionless_count"] < camera_config.detect.stationary.threshold
        and o["position_changes"] > 0
        and o["frame_time"] == frame_time
        and not o["false_positive"]
    ]