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• Seeking with ffmpeg options fails or causes delayed playback in Discord bot

  29 août 2022, par J Petersen

  My Discord bot allows users to play a song starting from a timestamp.

  


  The problem is that playback is delayed and audio plays faster and is jumbled if start times >= 30s are set.

  


  Results from testing different start times. Same URL, 30 second duration :

  


  





  


  


  


  


  


  



  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  


  Entered Start Time (s)	Playback Delay (s)	Song Playback Time (s)
  0	3	30
  30	10	22
  60	17	17
  120	31	2
  150	120	<1

  


  


  I am setting the start time using ffmpeg_options as suggested in this question.

  


  Does anyone understand why the audio playback is being delayed/jumbled ? How can I improve playback delay and allow users to start in the middle of a multi-chapter YouTube video ?

  


  Code :

  


  import discord
import youtube_dl
import asyncio


# Suppress noise about console usage from errors
youtube_dl.utils.bug_reports_message = lambda: ""


ytdl_format_options = {
    "format": "bestaudio/best",
    "outtmpl": "%(extractor)s-%(id)s-%(title)s.%(ext)s",
    "restrictfilenames": True,
    "noplaylist": False,
    "yesplaylist": True,
    "nocheckcertificate": True,
    "ignoreerrors": False,
    "logtostderr": False,
    "quiet": True,
    "no_warnings": True,
    "default_search": "auto",
    "source_address": "0.0.0.0",  # Bind to ipv4 since ipv6 addresses cause issues at certain times
}

ytdl = youtube_dl.YoutubeDL(ytdl_format_options)


class YTDLSource(discord.PCMVolumeTransformer):
    def __init__(self, source: discord.AudioSource, *, data: dict, volume: float = 0.5):
        super().__init__(source, volume)

        self.data = data

        self.title = data.get("title")
        self.url = data.get("url")

    @classmethod
    async def from_url(cls, url, *, loop=None, stream=False, timestamp = 0):
        ffmpeg_options = {
            "options": f"-vn -ss {timestamp}"}

        loop = loop or asyncio.get_event_loop()

        data = await loop.run_in_executor(None, lambda: ytdl.extract_info(url, download=not stream))
        if "entries" in data:
            # Takes the first item from a playlist
            data = data["entries"][0]

        filename = data["url"] if stream else ytdl.prepare_filename(data)
        return cls(discord.FFmpegPCMAudio(filename, **ffmpeg_options), data=data)


intents = discord.Intents.default()

bot = discord.Bot(intents=intents)

@bot.slash_command()
async def play(ctx, audio: discord.Option(), seconds: discord.Option(), timestamp: discord.Option()):
    channel = ctx.author.voice.channel
    voice = await channel.connect()
    player = await YTDLSource.from_url(audio, loop=bot.loop, stream=True, timestamp=int(timestamp))
    voice.play(player)
    await asyncio.sleep(int(seconds))
    await voice.disconnect()

token = token value
bot.run(token)


  


• ffmpeg : programmatically use libavcodec and encode and decode raw bitmap, all in just few milliseconds and small compressed size on Raspberry Pi 4

  15 mars 2023, par Jerry Switalski

  We need to compress the size of the 1024x2048 image we produce, to size of about jpeg (200-500kb) from raw 32bits RGBA (8Mb) on Raspberry Pi 4. All in c/c++ program.

  


  The compression needs to be just in few milliseconds, otherwise it is pointless to us.

  


  We decided to try supported encoding using ffmpeg dev library and c/c++ code.

  


  The problem we are facing is that when we edited example of the encoding, provided by ffmpeg developers, the times we are dealing are unacceptable.

  


  Here you can see the edited code where the frames are created :

  


  for (i = 0; i < 25; i++)
{
#ifdef MEASURE_TIME
        auto start_time = std::chrono::high_resolution_clock::now();
        std::cout << "START Encoding frame...\n";
#endif
    fflush(stdout);

    ret = av_frame_make_writable(frame);
    if (ret < 0)
        exit(1);

    //I try here, to convert our 32 bits RGBA image to YUV pixel format:

    for (y = 0; y < c->height; y++)
    {
        for (x = 0; x < c->width; x++)
        {
            int imageIndexY = y * frame->linesize[0] + x;

            uint32_t rgbPixel = ((uint32_t*)OutputDataImage)[imageIndexY];

            double Y, U, V;
            uint8_t R = rgbPixel << 24;
            uint8_t G = rgbPixel << 16;
            uint8_t B = rgbPixel << 8;

            YUVfromRGB(Y, U, V, (double)R, (double)G, (double)B);
            frame->data[0][imageIndexY] = (uint8_t)Y;

            if (y % 2 == 0 && x % 2 == 0)
            {
                int imageIndexU = (y / 2) * frame->linesize[1] + (x / 2);
                int imageIndexV = (y / 2) * frame->linesize[2] + (x / 2);

                frame->data[1][imageIndexU] = (uint8_t)U;
                frame->data[2][imageIndexV] = (uint8_t)Y;
            }
        }
    }

    frame->pts = i;

    /* encode the image */
    encode(c, frame, pkt, f);

#ifdef MEASURE_TIME
        auto end_time = std::chrono::high_resolution_clock::now();
        auto time = end_time - start_time;
        std::cout << "FINISHED Encoding frame in: " << time / std::chrono::milliseconds(1) << "ms.\n";

#endif
    }


  


  Here are some important parts of the previous parts of that function :

  


  codec_name = "mpeg4";

codec = avcodec_find_encoder_by_name(codec_name);

c = avcodec_alloc_context3(codec);
    
c->bit_rate = 1000000;  
c->width = IMAGE_WIDTH;
c->height = IMAGE_HEIGHT;
c->gop_size = 1;
c->max_b_frames = 1;
c->pix_fmt = AV_PIX_FMT_YUV420P;   


  


  IMAGE_WIDTH and IMAGE_HEIGHT are 1024 and 2048 corresponding.

  


  The result I have ran on Raspberry Pi 4 look like this :

  


  START Encoding frame...
Send frame   0
FINISHED Encoding frame in: 40ms.
START Encoding frame...
Send frame   1
Write packet   0 (size=11329)
FINISHED Encoding frame in: 60ms.
START Encoding frame...
Send frame   2
Write packet   1 (size=11329)
FINISHED Encoding frame in: 58ms.


  


  Since I am completely green in encoding and using codecs, my question will be how to do it the best way and correct way, meaning the way which would reduce timing to few ms, and I am not sure the codec was chosen the best for the job, or the pixel format.

  


  The rest of the meaningful code you can see here (the encode() function you can find in the ffmpeg developer example I gave link to above) :

  


  void RGBfromYUV(double& R, double& G, double& B, double Y, double U, double V)
{
    Y -= 16;
    U -= 128;
    V -= 128;
    R = 1.164 * Y + 1.596 * V;
    G = 1.164 * Y - 0.392 * U - 0.813 * V;
    B = 1.164 * Y + 2.017 * U;
}


  


• avcodec/svq1enc : Add SVQ1EncDSPContext, make codec context private

  10 octobre 2022, par Andreas Rheinhardt

  avcodec/svq1enc : Add SVQ1EncDSPContext, make codec context private
  Currently, SVQ1EncContext is defined in a header that is also
  
  included by the arch-specific code that initializes the one
  
  and only dsp function that this encoder uses directly.
  But the arch-specific functions to set this dsp function
  
  do not need anything from SVQ1EncContext. This commit therefore
  
  adds a small SVQ1EncDSPContext whose only member is said
  
  function pointer and renames svq1enc.h to svq1encdsp.h
  
  to avoid exposing unnecessary internals to these init
  
  functions (and the whole mpegvideo with it).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/ppc/svq1enc_altivec.c
  • [DH] libavcodec/svq1enc.c
  • [DH] libavcodec/svq1enc.h
  • [DH] libavcodec/svq1encdsp.h
  • [DH] libavcodec/x86/svq1enc_init.c