feat: Add synchronization to start of audio recordings

[OmLanke]

Summary

When a Voice Channel is being recorded, users' recordings start when they start speaking, and not when the recording was actually started. This PR adds silence at the start of the recordings of users who weren't speaking when the recording started, but started speaking later.

This however relies on the receipt timestamp of the first packet, which can sometimes cause slightly inaccurate synchronisation, based on the network conditions.

This PR solves #1980.

Information

• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed).
• This PR is not a code change (e.g. documentation, README, typehinting,
  examples, ...).

Checklist

• I have searched the open pull requests for duplicates.
• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why.
• I have updated the changelog to include these changes.

[OmLanke]

I'll add an example for this too. For now, this is enough to test the merging of audio recordings-

import asyncio
import io

from pydub import AudioSegment # pip install pydub

import discord
from discord.ext import commands
from discord.sinks import MP3Sink


class MyCog(commands.Cog):
    def __init__(self, bot: commands.Bot):
        self.bot = bot

    async def finished_callback(
        self,
        sink: MP3Sink,
        channel: discord.TextChannel,
    ):
        mention_strs = []
        audio_segs: list[AudioSegment] = []
        files: list[discord.File] = []

        longest = AudioSegment.empty()

        for user_id, audio in sink.audio_data.items():

            mention_strs.append(f"<@{user_id}>")

            seg = AudioSegment.from_file(audio.file, format="mp3")

            # Determine the longest audio segment
            if len(seg) > len(longest):
                audio_segs.append(longest)
                longest = seg
            else:
                audio_segs.append(seg)

            audio.file.seek(0)
            files.append(discord.File(audio.file, filename=f"{user_id}.mp3"))

        for seg in audio_segs:
            longest = longest.overlay(seg)

        with io.BytesIO() as f:
            longest.export(f, format="mp3")
            await channel.send(
                f"Finished! Recorded audio for {', '.join(mention_strs)}.",
                files=files + [discord.File(f, filename="recording.mp3")],
            )

    @commands.command()
    async def join(self, ctx: commands.Context):
        await ctx.author.voice.channel.connect()

    @commands.command()
    async def record(self, ctx: commands.Context):
        vc: discord.VoiceClient = ctx.voice_client

        await ctx.send("Recording...")

        vc.start_recording(
            discord.sinks.MP3Sink(),
            self.finished_callback,
            ctx.channel,
            sync_start=True,
        )

        await asyncio.sleep(15) # edit to change recording duration
        vc.stop_recording()
        await ctx.send("Stopped recording.")


def setup(bot: commands.Bot):
    bot.add_cog(MyCog(bot))

[codecov]

Codecov Report

Merging #1984 (ecd3177) into master (4675c6c) will decrease coverage by 0.02%.
The diff coverage is 10.52%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1984      +/-   ##
==========================================
- Coverage   33.27%   33.25%   -0.02%     
==========================================
  Files          97       97              
  Lines       19017    19027      +10     
==========================================
  Hits         6328     6328              
- Misses      12689    12699      +10     

Flag	Coverage Δ
macos-latest-3.10	33.24% <10.52%> (-0.02%)	⬇️
macos-latest-3.11	33.24% <10.52%> (-0.02%)	⬇️
macos-latest-3.8	33.25% <10.52%> (-0.02%)	⬇️
macos-latest-3.9	33.25% <10.52%> (-0.02%)	⬇️
ubuntu-latest-3.10	33.24% <10.52%> (-0.02%)	⬇️
ubuntu-latest-3.11	33.24% <10.52%> (-0.02%)	⬇️
ubuntu-latest-3.8	33.25% <10.52%> (-0.02%)	⬇️
ubuntu-latest-3.9	33.25% <10.52%> (-0.02%)	⬇️
windows-latest-3.10	33.24% <10.52%> (-0.02%)	⬇️
windows-latest-3.11	33.24% <10.52%> (-0.02%)	⬇️
windows-latest-3.8	33.25% <10.52%> (-0.02%)	⬇️
windows-latest-3.9	33.25% <10.52%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
discord/sinks/core.py	40.00% <0.00%> (-0.43%)	⬇️
discord/voice_client.py	20.89% <11.11%> (-0.46%)	⬇️

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[Lulalaby]

Sigh

x

[plun1331]

@Lulalaby any updates?

[OmLanke]

@Lulalaby any updates?

Check this message by Lala in the discord server

[BobDotCom]

Please fix merge conflicts

[Lulalaby]

i rly had a stroke rn lol

[Lulalaby]

@plun1331 ping pong