Re: A2DP AAC codec bandwidth
Re: A2DP AAC codec bandwidth
- Subject: Re: A2DP AAC codec bandwidth
- From: Gordon Rankin <email@hidden>
- Date: Tue, 03 May 2016 15:33:26 -0400
- Organization: Wavelength Audio, ltd.
- X_cmae_category: , ,
- X_cmae_category: , ,
Craig,
I have to agree with Yuhon, it's an easy test to verify bandwidth and
the greater bandwidth has been proven in many a AES articles to give
better perceptual reproduction. But it's also easy to take an App like
Faber Acoustical SignalSuite and send various fixed waveforms (sine at
periodic or sweep) to an AAC (or SBC) endpoint and check quality with Ap
or Prism tests sets for distortion and SNR values relative to OS's versions.
A few months ago we had our MTU set low and testing proved poor response
on our endpoint. We upped the value to an acceptable level and saw a
huge improvement.
Thanks,
Gordon
Date: Tue, 03 May 2016 02:22:37 +0000
From: Feng Yu Hong <email@hidden>
To: "email@hidden" <email@hidden>
Cc: "email@hidden" <email@hidden>
Subject: Re: A2DP AAC codec bandwidth
Message-ID:
<email@hidden>
Content-Type: text/plain; charset="gb2312"
Thank for your reply.
I know AAC codec is perceptual codec, and subject listing test is best method of measuring perceptual quality. But lots customers take the codec bandwidth as an important objective evaluation index.
Is it possible that measuring codec bandwidth reaches 20kHz on IOS 9.2 if setting MTU value is more than 895 byte?
Yuhong
________________________________
发件人: email@hidden [mailto:email@hidden]
发送时间: 2016年4月30日 8:34
收件人: Feng Yu Hong
抄送: email@hidden
主题: Re: A2DP AAC codec bandwidth
How are you measuring quality? I’m not a codec engineer, but I would imagine you need a psychoacoustic test to measure “quality”. Bitrate or sample rate alone can tell you the data pattern, but it’s very possible that the AAC encoder has improved over time and can now encode the same data with similar or better perceived quality at the same or lower bitrates.
- Craig
--
J. Gordon Rankin
Owner and Chief Scientist
====== Wavelength Audio, ltd ======
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