Basic architecture to serve, stream and consume large audio files to minimize client-side resource consumption and latency

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I am trying to build a web application which will need to have audio streaming functionality implemented in some way. Just to give you guys some context: It is designed to be a purely auditive experience/game/idkhowtocallit with lots of different sound assets varying in length and thus file size. The sound assets to be provided will consist of ambient sounds, spoken bits of conversation, but also long music sets (up to a couple of hours). Why I think I won't be able to just host these audio files on some server or CDN and serve them from there is, because the sound assets will need to be fetched and played dynamically (depending on user interaction) and as instantly as possible.

  1. Most importantly, consuming larger files (like the music sets and long ambient loops) as a whole doesn't seem to be client-friendly at all to me (used data consumption on mobile networks and client-side memory usage).
  2. Also, without any buffering or streaming mechanism, the client won't be able to start playing these files before they are downloaded completely, right? Which would add the issue of high latencies.

I've tried to do some online research on how to properly implement a good infrastructure to stream bigger audio files to clients on the server side and found HLS and MPEG-DASH. I have some experience with consuming HLS players with web players and if I understand it correctly, I would use some sort of one-time transformation process (on or after file upload) to split up the files into chunks and create the playlist and then just serve these files via HTTP. From what I understand the process should be more or less the same for MPEG-DASH. My issue with these two techniques is that I couldn't really find any documentation on how to implement JavaScript/TypeScript clients (particularly using the Web Audio API) without reinventing the wheel. My best guess would be to use something like hls.js and bind the HLS streams to freshly created audio elements and use these elements to create AudioSources in my Web Audio Graph. How far off am I? I'm trying to get at least an idea of a best practice.

To sum up what I would really appreciate to get some clarity about:

  1. Would HLS or MPEG-DASH really be the way to go or am I missing a more basic chunked file streaming mechanism with good libraries?
  2. How - theoretically - would I go about limiting the amount of chunks downloaded in advance on the client side to save client-side resources, which is one of my biggest concerns?
  3. I was looking into hosting services as well, but figured that most of them are specialized in hosting podcasts (fewer but very large files). Has anyone an opinion about whether I could use these services to host and stream possibly 1000s of files with sizes ranging from very small to rather large?

Thank you so much in advance to everyone who will be bothered with helping me out. Really appreciate it.

audio-player http-live-streaming web-audio-api html5-audio audio-streaming
1 Answers

Why I think I won't be able to just host these audio files on some server or CDN and serve them from there is, because the sound assets will need to be fetched and played dynamically (depending on user interaction) and as instantly as possible.

Your long running ambient sounds can stream, using a normal HTMLAudioElement. When you play them, there may be a little lag time before they start since they have to begin streaming, but note that the browser will generally prefetch the metadata and maybe even the beginning of the media data.

For short sounds where latency is critical (like one-shot user interaction sound effects), load those into buffers with the Web Audio API for playback. You won't be able to stream them, but they'll play as instantly as you can get.

Most importantly, consuming larger files (like the music sets and long ambient loops) as a whole doesn't seem to be client-friendly at all to me (used data consumption on mobile networks and client-side memory usage).

If you want to play the audio, you naturally have to download that audio. You can't play something you haven't loaded in some way. If you use an audio element, you won't be downloading much more than what is being played. And, that downloading is mostly going to occur on-demand.

Also, without any buffering or streaming mechanism, the client won't be able to start playing these files before they are downloaded completely, right? Which would add the issue of high latencies.

If you use an audio element, the browser takes care of all the buffering and what not for you. You don't have to worry about it.

I've tried to do some online research on how to properly implement a good infrastructure to stream bigger audio files to clients on the server side and found HLS and MPEG-DASH.

If you're only streaming a single bitrate (which for audio is usually fine) and you're not streaming live content, then there's no point to HLS or DASH here.

Would HLS or MPEG-DASH really be the way to go or am I missing a more basic chunked file streaming mechanism with good libraries?

The browser will make ranged HTTP requests to get the data it needs out of the regular static media file. You don't need to do anything special to stream it. Just make sure your server is configured to handle ranged requests... most any should be able to do this right out of the box.

How - theoretically - would I go about limiting the amount of chunks downloaded in advance on the client side to save client-side resources, which is one of my biggest concerns?

The browser does this for you if you use an audio element. Additionally, data saving settings and the detected connectivity speed may impact whether or not the browser pre-fetches. The point is, you don't have to worry about this. You'll only be using what you need.

Just make sure you're compressing your media as efficiently as you can for the required audio quality. Use a good codec like Opus or AAC.

I was looking into hosting services as well, but figured that most of them are specialized in hosting podcasts (fewer but very large files). Has anyone an opinion about whether I could use these services to host and stream possibly 1000s of files with sizes ranging from very small to rather large?

Most any regular HTTP CDN will work just fine.

One final note for you... beware of iOS and Safari. Thanks to Apple's restrictive policies, all browsers under iOS are effectively Safari. Safari is incapable of playing more than one audio element at a time. If you use the Web Audio API you have more flexibility, but the Web Audio API has no real provision for streaming. You can use a media element source node, but this breaks lock screen metadata and outright doesn't work on some older versions of iOS. TL;DR; Safari is all but useless for audio on the web, and Apple's business practices have broken any alternatives.

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