Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752705AbaJ1NSd (ORCPT ); Tue, 28 Oct 2014 09:18:33 -0400 Received: from mailapp01.imgtec.com ([195.59.15.196]:50000 "EHLO mailapp01.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751575AbaJ1NSc (ORCPT ); Tue, 28 Oct 2014 09:18:32 -0400 Message-ID: <544F97A4.7080209@imgtec.com> Date: Tue, 28 Oct 2014 13:18:28 +0000 From: Qais Yousef User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.8.0 MIME-Version: 1.0 To: Clemens Ladisch , CC: Arnd Bergmann , Greg Kroah-Hartman , , , Neil Jones Subject: Re: [PATCH 00/11] Add AXD Audio Processing IP driver References: <1414495589-8579-1-git-send-email-qais.yousef@imgtec.com> <544F8439.4080402@ladisch.de> In-Reply-To: <544F8439.4080402@ladisch.de> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.154.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/28/2014 11:55 AM, Clemens Ladisch wrote: > Qais Yousef wrote: >> AXD Audio Processing IP performs audio decoding, encoding, mixing, equalisation, >> synchronisation and playback. > What exactly do you mean with "synchronisation" and "playback"? Synchronisation refers to accurate audio playout relative to a master clock source including compensation of drift between the master clock source and the playout clock of the audio hardware. Hence allowing synchronised audio playout across multiple independent devices. Playback simple refers to the fact that AXD is capable of managing audio playout hardware like I2S and SPDIF interfaces. >> It doesn't fit in alsa subsystem but I Cced them to confirm. > ... because those two words sound like something that a sound card could do. The problem mainly stems from the fact that we take a variety of compressed audio as input and we could perform audio encoding. The problem with the compressed audio is that the range of decoders and configuration supported in alsa is limited and there's no support for taking raw pcm and producing compressed output. I'm not an expert on alsa but when I looked it looked like there's more infra structure required. The following not supported points from Documentation/sound/alsa/compress_offload.txt affect us: - Volume control/routing is not handled by this API. Devices exposing a compressed data interface will be considered as regular ALSA devices; volume changes and routing information will be provided with regular ALSA kcontrols. - Embedded audio effects. Such effects should be enabled in the same manner, no matter if the input was PCM or compressed. - Encoding/decoding acceleration is not supported as mentioned above. It is possible to route the output of a decoder to a capture stream, or even implement transcoding capabilities. This routing would be enabled with ALSA kcontrols. >> I added it to drivers/char as this is the best location I could think of at the >> moment. > drivers/misc? Yeah could do if there's consensus. Thanks, Qais > > Regards, > Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/