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Topic: High end frequencies sound horrible on stream (Read 5454 times) previous topic - next topic
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High end frequencies sound horrible on stream

Hi all

I have an issue with an AAC+ stream I'm using for FM broadcast.

THe stream is 64kbps mono. Due to limitations at the broadcast site (and indications from the AAC+ community that it would be better to do it this way so as to not mess up the compression on the audio when its processed), the audio processing must be done at the studio.

The audio is being passed through a line in plugin, into winamp, processed with a dsp processor and on to the shoutcast plug in.

The audio comming from the processor sounds good. However the stream sounds woeful. The highend is being completely garbled and sounds awful.

Does anyone know exactly whats causing this?

The stream can be listened to here (apologies for the music):
http://cp.internet-radio.org.uk/tunein.php...07/playlist.pls


Just wait for any high frequency note and you'll hear it straight away.

All replies appreciated.
(I've also posted this while drunk, so apologies for anything/everything that I may have inadvertantly put in this post)
Baker

High end frequencies sound horrible on stream

Reply #1 –
For anyone who attempted to listen to the stream and it was off, its back up now.

Guru Josh - Infinity is playing, and the bit with the violin like music is horrible. The encoder is really distorting it.

Baker

High end frequencies sound horrible on stream

Reply #2 –
Just be to be sure - you are aware of the fact, that AAC+ does not transfer high frequencies, but instead reproduces them using SBR? It might sound better or worse, depending on the content.

For me, this stream sound quite normal for 64kbps AAC+...
IMHO it should be streamed stereo with such bitrate and codec, giving more fidelity overall.
Not really a Signature.

High end frequencies sound horrible on stream

Reply #3 –
Quote from: vitos on
Just be to be sure - you are aware of the fact, that AAC+ does not transfer high frequencies, but instead reproduces them using SBR? It might sound better or worse, depending on the content.

For me, this stream sound quite normal for 64kbps AAC+...
IMHO it should be streamed stereo with such bitrate and codec, giving more fidelity overall.


The broadcast is Mono only.
Using stereo for the stream would be pointless and a waste of bitrate.

Whats throwing me is that these artifacts only seem to appear when the sound processing is being used.

I think ill just switch to a different format.

Baker

High end frequencies sound horrible on stream

Reply #4 –
At 64kbps for mono content, AAC-LC ("normal AAC") should be pretty good most of the time (though I'm mostly aware of VBR quality, not streamed CBR) and will attempt to faithfully reproduce frequencies above 11kHz rather than "guess them", all the way up to the lowpass used.

Even MP3 at 64 kbps mono should be capable of very decent sound with near-universal compatibility.
Dynamic – the artist formerly known as DickD

High end frequencies sound horrible on stream

Reply #5 –
Quote from: Dynamic on
At 64kbps for mono content, AAC-LC ("normal AAC") should be pretty good most of the time (though I'm mostly aware of VBR quality, not streamed CBR) and will attempt to faithfully reproduce frequencies above 11kHz rather than "guess them", all the way up to the lowpass used.

Even MP3 at 64 kbps mono should be capable of very decent sound with near-universal compatibility.

Evidently AAC LC isn't supported in shoutcast. Although the option is there it won't stream. I've been advised by the winamp guys that it won't work.

Switched to 32khz MONO 64kbps MP3. Sounds great!

Baker

High end frequencies sound horrible on stream

Reply #6 –
Quote from: muxer107 on
Evidently AAC LC isn't supported in shoutcast.


You said it supports AAC+ (really HE-AAC), which is a superset of LC AAC, so that makes no sense.

Quote
I've been advised by the winamp guys that it won't work.


Then Winamp is really completely broken.

High end frequencies sound horrible on stream

Reply #7 –
Quote from: muxer107 on
The broadcast is Mono only.
Using stereo for the stream would be pointless and a waste of bitrate.


Not at all, I don't understand why you think that. Using stereo doesn't use twice the bitrate (for the same quality), and 64kbps is more than enough to get stereo. The only reason not to use stereo here is if the source is mono.

What encoder is used?

High end frequencies sound horrible on stream

Reply #8 –
Quote from: Garf on
Quote from: muxer107 on
The broadcast is Mono only.
Using stereo for the stream would be pointless and a waste of bitrate.


Not at all, I don't understand why you think that. Using stereo doesn't use twice the bitrate (for the same quality), and 64kbps is more than enough to get stereo. The only reason not to use stereo here is if the source is mono.

What encoder is used?


I know that using stereo doesn't double the bit-rate. I understand the basics of how stereo information is used in lossy encoding.

The stream is to be outputted in mono. There is no point using bits to hold stereo information when it'll never be heard!

Heres the link for the winamp forum post where I was told that AAC LC wasn't supported for streaming:
http://forums.winamp.com/showthread.php?threadid=311807

Baker

High end frequencies sound horrible on stream

Reply #9 –
Quote from: muxer107 on
The stream is to be outputted in mono.


Any particular reason for that?
I hate to listen to mono music, but that's just my opinion.
Not really a Signature.
 

High end frequencies sound horrible on stream

Reply #10 –
Quote from: vitos on
Quote from: muxer107 on
The stream is to be outputted in mono.


Any particular reason for that?
I hate to listen to mono music, but that's just my opinion.


The broadcast is Mono. We have a low power license and stereo broadcast would reduce our range and stereo would drop in and out. Mono will just sound better

Baker