Av1an/Encoders/encoder.py

from abc import ABC, abstractmethod
from distutils.spawn import find_executable
from typing import Tuple, Optional
import subprocess
from subprocess import PIPE, STDOUT, DEVNULL

from Av1an.arg_parse import Args
from Chunks.chunk import Chunk
from Av1an.commandtypes import Command, MPCommands


class Encoder(ABC):
    """
    An abstract class used for encoders
    """

    def __init__(self, encoder_bin: str, encoder_help: str, default_args: Command, default_passes: int, default_q_range: Tuple[int, int],
                 output_extension: str):
        """
        Encoder constructor

        :param encoder_bin: the binary for the encoder
        :param default_args: the default cli args for the encoder
        :param output_extension: the output extension (no dot)
        """
        self.encoder_bin = encoder_bin
        self.encoder_help = encoder_help
        self.default_args = default_args
        self.default_passes = default_passes
        self.default_q_range = default_q_range
        self.output_extension = output_extension

    @staticmethod
    def compose_ffmpeg_pipe(a: Args) -> Command:
        """
        Creates an ffmpeg pipe command for the args

        :param a: the Args
        :return: an ffmpeg command that will pipe into the encoder
        """
        return ['ffmpeg', '-y', '-hide_banner', '-loglevel', 'error', '-i', '-', *a.ffmpeg_pipe]

    @abstractmethod
    def compose_1_pass(self, a: Args, c: Chunk, output: str) -> MPCommands:
        """
        Composes the commands needed for a 1 pass encode

        :param a: the Args
        :param c: the Chunk
        :param output: path for encoded output
        :return: a MPCommands object (a list of CommandPairs)
        """
        pass

    @abstractmethod
    def compose_2_pass(self, a: Args, c: Chunk, output: str) -> MPCommands:
        """
        Composes the commands needed for a 2 pass encode

        :param a: the Args
        :param c: the Chunk
        :param output: path for encoded output
        :return: a MPCommands object (a list of CommandPairs)
        """
        pass

    @abstractmethod
    def man_q(self, command: Command, q: int) -> Command:
        """Return command with new cq value

        :param command: old command
        :param q: new cq value
        :return: command with new cq value"""
        pass

    @abstractmethod
    def match_line(self, line: str):
        """Extract number of encoded frames from line.

        :param line: one line of text output from the encoder
        :return: match object from re.search matching the number of encoded frames"""
        pass

    def make_pipes(self, a: Args, c: Chunk, passes: int, current_pass: int, output: str, man_q: int = None):
        """
        Creates a pipe for the given chunk with the given args

        :param a: the Args
        :param c: the Chunk
        :param passes: the total number of passes (1 or 2)
        :param current_pass: the current_pass
        :param output: path posix string for encoded output
        :param man_q: use a different quality
        :return: a Pipe attached to the encoders stdout
        """
        filter_cmd, enc_cmd = self.compose_1_pass(a, c, output)[0] if passes == 1 else \
                              self.compose_2_pass(a, c, output)[current_pass - 1]

        if man_q:
            enc_cmd = self.man_q(enc_cmd, man_q)
        elif c.vmaf_target_cq:
            enc_cmd = self.man_q(enc_cmd, c.vmaf_target_cq)

        ffmpeg_gen_pipe = subprocess.Popen(c.ffmpeg_gen_cmd, stdout=PIPE, stderr=DEVNULL)
        ffmpeg_pipe = subprocess.Popen(filter_cmd, stdin=ffmpeg_gen_pipe.stdout, stdout=PIPE, stderr=STDOUT)
        pipe = subprocess.Popen(enc_cmd, stdin=ffmpeg_pipe.stdout, stdout=PIPE,
                                stderr=STDOUT,
                                universal_newlines=True)

        return pipe

    def is_valid(self, args: Args) -> Tuple[bool, Optional[str]]:
        """
        Determines if the encoder is properly set up. Checkes to make sure executable exists and args are all compatible
        with this encoder.
        :param args: the Args
        :return: A tuple of (status, error). Status is false and error is set if encoder is not valid
        """
        if not self.check_exists():
            return False, f'Encoder {self.encoder_bin} not found. Is it installed in the system path?'
        return True, None

    def check_exists(self) -> bool:
        """
        Verifies that this encoder exists in the system path and is ok to use
        :return: True if the encoder bin exists
        """
        return find_executable(self.encoder_bin) is not None

    def on_before_chunk(self, args: Args, chunk: Chunk) -> None:
        """
        An event that is called before the encoding passes of a chunk starts
        :param args: the Args
        :param chunk: the chunk
        :return: None
        """
        pass

    def on_after_chunk(self, args: Args, chunk: Chunk) -> None:
        """
        An event that is called after the encoding passes of a chunk completes
        :param args: the Args
        :param chunk: the chunk
        :return: None
        """
        pass

    def __eq__(self, o: object) -> bool:
        """
        Supports equality of encoders based on encoder_bin

        :param o: other object
        :return: True iff o is an EncoderBC and self.encoder_bin == o.encoder_bin
        """
        if not isinstance(o, Encoder):
            return False
        return self.encoder_bin == o.encoder_bin