changed decoder from a thread into an iterator

video2x/decoder.py

@@ -19,22 +19,15 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
 Name: Video Decoder
 Author: K4YT3X
 Date Created: June 17, 2021
-Last Modified: March 21, 2022
+Last Modified: April 9, 2022
 """
 
-import contextlib
-import multiprocessing
 import os
 import pathlib
-import queue
 import signal
 import subprocess
-import threading
-import time
-from multiprocessing.sharedctypes import Synchronized
 
 import ffmpeg
-from loguru import logger
 from PIL import Image
 
 from .pipe_printer import PipePrinter
@@ -51,32 +44,34 @@ LOGURU_FFMPEG_LOGLEVELS = {
 }
 
 
-class VideoDecoder(threading.Thread):
+class VideoDecoder:
+    """
+    A video decoder that generates frames read from FFmpeg.
+
+    :param input_path pathlib.Path: the input file's path
+    :param input_width int: the input file's width
+    :param input_height int: the input file's height
+    :param frame_rate float: the input file's frame rate
+    :param pil_ignore_max_image_pixels bool: setting this to True
+        disables PIL's "possible DDoS" warning
+    """
+
     def __init__(
         self,
         input_path: pathlib.Path,
         input_width: int,
         input_height: int,
         frame_rate: float,
-        processing_queue: multiprocessing.Queue,
-        processing_settings: tuple,
-        pause: Synchronized,
-        ignore_max_image_pixels=True,
+        pil_ignore_max_image_pixels: bool = True,
     ) -> None:
-        threading.Thread.__init__(self)
-        self.running = False
         self.input_path = input_path
         self.input_width = input_width
         self.input_height = input_height
-        self.processing_queue = processing_queue
-        self.processing_settings = processing_settings
-        self.pause = pause
 
         # this disables the "possible DDoS" warning
-        if ignore_max_image_pixels:
+        if pil_ignore_max_image_pixels is True:
             Image.MAX_IMAGE_PIXELS = None
 
-        self.exception = None
         self.decoder = subprocess.Popen(
             ffmpeg.compile(
                 ffmpeg.input(input_path, r=frame_rate)["v"]
@@ -102,75 +97,27 @@ class VideoDecoder(threading.Thread):
         self.pipe_printer = PipePrinter(self.decoder.stderr)
         self.pipe_printer.start()
 
-    def run(self) -> None:
-        self.running = True
+    def __iter__(self):
 
-        # the index of the frame
-        frame_index = 0
-
-        # create placeholder for previous frame
-        # used in interpolate mode
-        previous_image = None
-
-        # continue running until an exception occurs
-        # or all frames have been decoded
-        while self.running is True:
-
-            # pause if pause flag is set
-            if self.pause.value is True:
-                time.sleep(0.1)
-                continue
-
-            try:
-                buffer = self.decoder.stdout.read(
+        # continue yielding while FFmpeg continues to produce output
+        while (
+            len(
+                buffer := self.decoder.stdout.read(
                     3 * self.input_width * self.input_height
                 )
-
-                # source depleted (decoding finished)
-                # after the last frame has been decoded
-                # read will return nothing
-                if len(buffer) == 0:
-                    self.stop()
-                    continue
+            )
+            > 0
+        ):
 
             # convert raw bytes into image object
-                image = Image.frombytes(
+            frame = Image.frombytes(
                 "RGB", (self.input_width, self.input_height), buffer
             )
 
-                # keep checking if the running flag is set to False
-                # while waiting to put the next image into the queue
-                while self.running is True:
-                    with contextlib.suppress(queue.Full):
-                        self.processing_queue.put(
-                            (
-                                frame_index,
-                                (previous_image, image),
-                                self.processing_settings,
-                            ),
-                            timeout=0.1,
-                        )
-                        break
+            # return this frame
+            yield frame
 
-                previous_image = image
-                frame_index += 1
-
-            # most likely "not enough image data"
-            except ValueError as error:
-                self.exception = error
-
-                # ignore queue closed
-                if "is closed" not in str(error):
-                    logger.exception(error)
-                break
-
-            # send exceptions into the client connection pipe
-            except Exception as error:
-                self.exception = error
-                logger.exception(error)
-                break
-        else:
-            logger.debug("Decoding queue depleted")
+    def __del__(self):
 
         # flush the remaining data in STDOUT and STDERR
         self.decoder.stdout.flush()
@@ -190,9 +137,3 @@ class VideoDecoder(threading.Thread):
         # wait for PIPE printer to exit
         self.pipe_printer.stop()
         self.pipe_printer.join()
-
-        logger.info("Decoder thread exiting")
-        return super().run()
-
-    def stop(self) -> None:
-        self.running = False