From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raymond Subject: Re: ALSA features. Date: Mon, 05 Sep 2005 14:00:40 +0800 Message-ID: <431BDF08.3090907@netvigator.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: alsa-devel-admin@lists.sourceforge.net Errors-To: alsa-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: alsa-devel@lists.sourceforge.net List-Id: alsa-devel@alsa-project.org I am looking for ALSA applications (signal generator and spectrum analyser) for measuring/calibrating the proposed au88x0 PCM volume control (per substream) and the existing hardware 10-bands stereo EQ controls on au8810/au8830 ALSA driver. The graphic equalizer program periodically reads the EQ peaks from the hardware registers and display them as 20 VU meters in real-time. There are 10 x 2 (left/right) volume control for the gain/atten of the 10 octave bands( 31Hz, 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, 8000Hz, 16000Hz) There is no datasheet for au88x0. Only front channels of au8810/au8830 pass through hardware mixer and the hardware equalizer, the rear channels of au8810/au8830 pass through hardware mixer only. The au8820 do not has equalizer. The 16-bits audio data passed through the hardware mixer of au88x0 to 18-bits DAC of AC97 codec. Any excess gain of the audio by increasing the hardware mixer volume cause distortion. Based on this assumption, please correct me if I am wrong. We assume the change of a value of 8 in hardware mixer volume is equal to (6dB) the gain of the 16-bits audio to 18-bits DAC. How can I perform test to prove this assumption ? The existing EQ controls allow us to increase/decrease the volume of individual bands. By decreasing all bands to zero, no sound is heard from the front channels and the corresponding VU meter also varies when changing the EQ cotnrol How can I measure/calibrate the EQ volume controls in dB ? Any other methods beside using signal generator/spectrum analyser ? James Courtier-Dutton wrote: > Hi, > > I am an ALSA developer and I was wondering if there are any feature requests that people who use this list would have. > > I currently have a lot on my TODO list, but there is probably only one feature on that list that might help you and that is dB level readouts in alsamixer. > > Currently, alsamixer uses a 0-100% readout, and on some sound cards 100% is the 0dB level, and on others the 0dB level is around 80%. > > This makes setting the capture levels rather difficult to get right in Ardour. Most people would want the alsamixer capture volume controls to all be set to 0dB and then let Ardour do any volume control. > > Any other suggestions? > > James ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf