lazy-player/lazy_player/thumbnailer.py

from __future__ import annotations

import multiprocessing
import os
import sys
from concurrent.futures import ThreadPoolExecutor
from queue import LifoQueue
from typing import TYPE_CHECKING, Any, cast

from gi.repository import GLib, Gst

if TYPE_CHECKING:
    from .file_model import FileItem

DEFAULT_SEEK_FLAGS = (
    Gst.SeekFlags.FLUSH
    | Gst.SeekFlags.KEY_UNIT
    | Gst.SeekFlags.SNAP_NEAREST
    | Gst.SeekFlags.TRICKMODE
    | Gst.SeekFlags.TRICKMODE_KEY_UNITS
    | Gst.SeekFlags.TRICKMODE_NO_AUDIO
)

__all__ = ["Thumbnailer", "generate_thumbnail_sync"]


MAX_WORKERS = max(1, multiprocessing.cpu_count() // 2)


class Thumbnailer(ThreadPoolExecutor):
    def __init__(self):
        super().__init__(
            thread_name_prefix="Thumbnailer",
            max_workers=MAX_WORKERS,
        )

        self._work_queue = cast(Any, LifoQueue())

    def generate_thumbnail(self, file_item: FileItem):
        """Schedule thumbnail generation."""

        if not file_item.full_path.is_file():
            return

        if file_item.attempted_thumbnail.value:
            return

        self.submit(generate_thumbnail_sync_nicely, file_item)
        file_item.attempted_thumbnail.value = True


def generate_thumbnail_sync_nicely(file_item: FileItem):
    os.nice(10)
    return generate_thumbnail_sync(file_item)


def generate_thumbnail_sync(file_item: FileItem):
    """Generate thumbnail for a single file"""

    # print("[thumbnailer] Generate:", file_item.full_path.name)

    pipeline_str = (
        "uridecodebin name=uridecodebin force-sw-decoders=true ! "
        "videoconvert ! "
        "jpegenc quality=85 ! "
        "appsink sync=false name=sink"
    )

    pipeline: Gst.Pipeline | None = None

    try:
        pipeline = cast(Gst.Pipeline, Gst.parse_launch(pipeline_str))

        sink = pipeline.get_by_name("sink")
        assert isinstance(sink, Gst.Element)

        uridecodebin = pipeline.get_by_name("uridecodebin")
        assert isinstance(uridecodebin, Gst.Element)

        # Set file URI
        uridecodebin.set_property("uri", Gst.filename_to_uri(str(file_item.full_path)))

        # Set pipeline to PAUSED to get duration
        pipeline.set_state(Gst.State.PAUSED)
        pipeline.get_state(Gst.CLOCK_TIME_NONE)

        # Obtain total duration
        success, duration = pipeline.query_duration(Gst.Format.TIME)
        if not success:
            raise RuntimeError("Failed to query duration")

        def get_sample(seek_pos: int) -> bytes:
            pipeline.seek_simple(Gst.Format.TIME, DEFAULT_SEEK_FLAGS, seek_pos)

            # Start playing to capture frame
            pipeline.set_state(Gst.State.PLAYING)

            sample = sink.emit("pull-sample")
            if not sample:
                raise RuntimeError("Failed to pull sample")

            # Extract image data
            buffer = sample.get_buffer()
            if not buffer:
                raise RuntimeError("Failed to get buffer")

            success, map_info = buffer.map(Gst.MapFlags.READ)
            if not success:
                raise RuntimeError("Failed to map buffer")

            try:
                return bytes(map_info.data)
            finally:
                buffer.unmap(map_info)

        candidates: list[bytes] = []

        for i in range(3):
            candidates.append(get_sample(duration // 3 - Gst.SECOND + i * Gst.SECOND))

        thumbnail = max(candidates, key=len)

        def set_thumbnail():
            file_item.thumbnail.value = thumbnail

        GLib.idle_add(set_thumbnail)

    except Exception as err:
        print("[thumbnailer] Error:", file_item.full_path.name, file=sys.stderr)
        print("[thumbnailer]", err, file=sys.stderr)

    finally:
        if pipeline:
            pipeline.set_state(Gst.State.NULL)