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• What are the correct conversion steps to generate a video from PDF with ffmpeg and mp4box

  25 juin 2020, par Michael Rall

  I need to convert a PDF-Document to a DASH-compatible stream. Every page of the PDF should be displayed for one second. Quality should be rather good, so that text and line graphics can still be read clearly. Additionally I want to be able to seek every page, so keyframes(?) should be (exactly) every second.

  


  Im using poppler-tools to extract the pdf-pages as png's -> works

  


  Im using ffmpeg to convert the single images to an x264 encoded mp4 video -> works (but maybe problematic)

  


  string.Format("-r 1 -i \"{0}.page_%d.png\" -r 24 -vcodec libx264 -pix_fmt yuv420p {0}.output.mp4", basePath)


  


  Im using MP4Box to convert that video to dash -> works (but needs improvement)

  


  string.Format("-dash 1000 -frag 1000 -rap -segment-name {1}_dash_$RepresentationID$_$Number$ -url-template {0}.output.mp4 -out \"{0}.{2}\"", basePath, tempDataId, STREAM_MANIFEST_FILE_POSTFIX)


  


  Now I have 2 Problems/Questions

  


  

  1. Are the settings for framerate, quality, outputformat correct for the goals I want to achieve

  


  2. When displaying the resulting DASH-Stream in the Demo-Player from https://github.com/Dash-Industry-Forum/dash.js/wiki it plays the stream, but as soon as I try to seek the player starts loading forever. Setting the position to start and let it play again works. The network tab in my browser-debugger shows that the player tries to load the segments and gets them successfully.

  


  


  I guess its a problem with keyframes, fragments or similar. Can somebody correct my conversion steps ?

  


  kind regards

  


• Understanding ffmpeg map option

  7 avril 2021, par Austin Kyker

  I came across the following command in a blog post which creates different quality video streams that are packaged into DASH format via the dash muxer.

  


  ffmpeg -i $VIDEO_IN \
    -preset $PRESET_P -keyint_min $GOP_SIZE -g $GOP_SIZE -sc_threshold 0 \
    -r $FPS -c:v libx264 -pix_fmt yuv420p -c:a aac -b:a 128k -ac 1 -ar 44100 \
    -map v:0 -s:0 $V_SIZE_1 -b:v:0 2M -maxrate:0 2.14M -bufsize:0 3.5M \
    -map v:0 -s:1 $V_SIZE_2 -b:v:1 145k -maxrate:1 155k -bufsize:1 220k \
    -map v:0 -s:2 $V_SIZE_3 -b:v:2 365k -maxrate:2 390k -bufsize:2 640k \
    -map v:0 -s:3 $V_SIZE_4 -b:v:3 730k -maxrate:3 781k -bufsize:3 1278k \
    -map v:0 -s:4 $V_SIZE_4 -b:v:4 1.1M -maxrate:4 1.17M -bufsize:4 2M \
    -map v:0 -s:5 $V_SIZE_5 -b:v:5 3M -maxrate:5 3.21M -bufsize:5 5.5M \
    -map v:0 -s:6 $V_SIZE_5 -b:v:6 4.5M -maxrate:6 4.8M -bufsize:6 8M \
    -map v:0 -s:7 $V_SIZE_6 -b:v:7 6M -maxrate:7 6.42M -bufsize:7 11M \
    -map v:0 -s:8 $V_SIZE_6 -b:v:8 7.8M -maxrate:8 8.3M -bufsize:8 14M \
    -map 0:a \
    -init_seg_name init\$RepresentationID\$.\$ext\$ -media_seg_name chunk\$RepresentationID\$-\$Number%05d\$.\$ext\$ \
    -use_template 1 -use_timeline 1  \
    -seg_duration 4 -adaptation_sets "id=0,streams=v id=1,streams=a" \
    -f dash Dash/dash.mpd


  


  The thing I'm struggling to understand is how the maps work. I've read the Map docs but they don't seem to have a comparable example.

  


  

  1. Why is -map v:0 used for every video stream ?

  


  2. Why does the first map line operate on stream 0 (e.g. -b:v:0) and the next map line operates on stream 1 (e.g. -b:v:1), etc.

  


  


  Would really appreciate a breakdown.

  


• How do I playback .m4s files. And turn them into a binary stream for a Discord Bot

  30 octobre 2020, par Harvey

  I want to download the BBC radio 2 and stream it to a discord server. Each request is https://as-dash-uk-live.akamaized.net/pool_904/live/uk/bbc_radio_two/bbc_radio_two.isml/dash/bbc_radio_two-audio=320000-250636302.m4s However the Time stamp will change and they regularly delete content. I found a .dash file as well https://as-dash-uk-live.akamaized.net/pool_904/live/uk/bbc_radio_two/bbc_radio_two.isml/dash/bbc_radio_two-audio=320000.dash which is seems to request. However I can't find how to send it through a discord bot to a discord server. My code is

  


  const axios = require('axios')


module.exports = {
    play: async function (guild,message) {
        const serverQueue = {};
        const voiceChannel = message.member.voice.channel
        serverQueue.connection = await voiceChannel.join();
        plays(guild)
        
        async function plays(guild) {
            let data1 = new Date(1353439725);
            let data2 = new Date(Date.now()/1000);
            console.log(`https://as-dash-uk-live.akamaized.net/pool_904/live/uk/bbc_radio_two/bbc_radio_two.isml/dash/bbc_radio_two-audio=320000-${Math.floor((data2 - data1))-4000}.m4s`)
            const dispatcher = serverQueue.connection.play((await axios.get(`https://as-dash-uk-live.akamaized.net/pool_904/live/uk/bbc_radio_two/bbc_radio_two.isml/dash/bbc_radio_two-audio=320000-${Math.floor((data2 - data1))-4000}.m4s`)).data)
                .on('finish', () => {
                    console.log('Music ended!');
                    plays(guild);
                    return
                })
                .on('error', error => {
                    console.error(error);
                    plays(guild);
                    return
                });
            dispatcher.setVolumeLogarithmic(serverQueue.volume / 5);
        }
    }
}


  


  However no audio plays and the audio end event is always being called. Am I being really stupid or is there a way to do this.