What is the expected size of the cover art in the broadcast, if available?
What does an ADTS stream mean?
https://en.wikipedia.org/wiki/Advanced_Audio_Coding
Does it mean Audio Data Transport System? If so, what is that? Does that mean, and I'm not sure if this question makes sense, aac is an internet media type?
More to the point, if you can broadcast in aac, is there a file type besides m3u that can act as the stream redirector for Windows/Mac/Linux? pls or asx? or is .aac its own stream redirector?
Cover Art and broadcasting doesn't seem to go hand in hand, at least in the classic sense of audio broadcasting. Sure, applications like Spotify show you covert art and other information, but that does not come from the audio stream.
An ADTS stream is an AAC stream without a container. The common container for AAC audio is the MP4 container, used commonly to store, playback and even for broadcasting it.
Nowadays you should only find MPEG4 ADTS format files, although there existed an MPEG2 variant, deprecated (AFAIK, there was a change in a few header values that required the new format, and one could convert the MPEG2 variant to the MPEG4 variant).
I am not sure what to reply to your last question. That would depend on the player used to playback those streams.
Generally m3u files where used when intended to be played by Winamp or Winamp-compatible players, whereas .pls was an alternate list. asx has mostly been used only for ASF streams although in essence it is also just a playlist and there are other programs that support it.
But no, aac is not a stream redirector. It is a raw stream.
What software for internet radio broadcast can broadcast in mp3 and aac and also can have the receiver use asx files? Preferably shoutcast? I want to set up my own LAN internet radio channel. Just to see how it works.
ASX is a playlist format, not a streaming protocol.
I have a shoutcast account now. What do I need to do to create a usable autohash for myself? I'm not sure shoutcast is allowing new channels.
I'm no expert, but I've done it in the past. There are usually 3 things to worry about when streaming:
Network Transport protocol
Container/Encapsulation format - (if any)
Audio/Video format
The network transport protocol is used to transfer the audio data from the media server to your player.
HTTP and RTP are two examples.
The container format contains additional information about the audio/video packets and is required to mux audio/video together.
The tricky part is knowing which audio/video format is compatible with which container format + network transfer protocols.
You might come up with a combination that is perfectly valid, but the player doesn't support the particular network transfer protocol or container format combination.
Only certain container formats support streaming. Some audio formats you can be streamed as raw data.
In the past I've used:
IceCast as the media server.
VLC or foobar2000(with a plugin) to stream audio to IceCast.
At the time AAC wasn't worth it since the quality of the the AAC encoders were really bad. Make sure it is fdkaac or else rather use libmp3lame.
The best results were achieved with Vorbis and Opus.
EDIT: If I had to do it now then I would use Liquidsoap and IceCast. Then specify multiple formats + bitrates to support a wide variety of players.
What I really am looing for is, what bit rate does an internet radio channel automatically start broadcasting cover art?
I wanted to run the experiment myself with a pier to pier internet radio channel, but this autohash thing is puzzling me.
What I really am looking for is, what bit rate does an internet radio channel automatically start broadcasting cover art?
I wanted to run the experiment myself with a pier to pier internet radio channel, but this autohash thing is puzzling me.
None at all. If I was able to do that then I tell you. I had problems with dynamic artist and track titles and decided to drop it for better server stability and ending the hang ups that would result in audible pauses on track changes.
Your main goal should be getting everything working well enough audio-wise and if you can and are able to do so without any issues proceed to send track title and artist info for your listeners. Forget album art, not even traditional FM broadcast stations bother sending that out over RDS nor does that sub-carrier even have the bandwidth for anything other than text.
I see it has become a subscription service.
I see it has become a subscription service.
Now, I see the question I really had in mind, if you use Shoutcast and/or SAM Broadcaster Pro, what file format do they deliver AAC streams to?
The internet radio we did as University students back in 2009, used Liquidsoap for stream generation and Icecast as media servers. Liquidsoap allows external encoders, which is what we used with FFmpeg, etc.
Liquidsoap also allows mixing live sources and media libraries, and can distribute to various servers, etc.
When it comes to ADTS: It's essentially a framing format for AAC, which then gets packed into an MPEG-TS stream. The reason being, that each frame is discernible by its header, so you can start playback of the stream anywhere, doesn't have to be from the start. MP4-files use MPEG-PS, which is Program Stream.
Things like album over art, supplemental information, etc. I've only seen reliably being used in DAB+, where a different picture is being sent once per minute or so, and it's part of the DAB+ metadata. Artist and track title are sent more often, such that the full information is sent once every three to five seconds or so. DAB+ subchannels have varying bandwidths, the lower bandwidth channels usually don't bother with pictures, album cover art, etc. or send one picture over three minutes or so, displaying the channel logo.