From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Lai Subject: Re: Compressed Audio Playback/Capture through ALSA framework Date: Tue, 15 Mar 2011 16:28:59 -0700 Message-ID: <4D7FF63B.40805@codeaurora.org> References: <4D7FB076.30300@codeaurora.org> <4D7FCEA3.4070003@audioscience.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D7FCEA3.4070003@audioscience.com> Sender: linux-arm-msm-owner@vger.kernel.org To: Eliot Blennerhassett Cc: alsa-devel , linux-arm-msm@vger.kernel.org List-Id: alsa-devel@alsa-project.org On 3/15/2011 1:40 PM, Eliot Blennerhassett wrote: > On 16/03/11 07:31, Patrick Lai wrote: >> Hi, >> >> Is there a precedent for playback/capture compressed audio stream >> through ALSA playback/capture interface if underlying hardware supports >> decoder + sink& encoder + source capabilities? > > No. (Apart from AC3 passthrough to spdif output) I presume you are referring to IEC958 format. Are there ASoC drivers that support IEC958 format already? Why is AC3 passthrough acceptable but not other compressed audio format? > ALSA might be extended to cope with compressed audio with fixed frame > size and bitrate, but dealing with any VBR encoding is likely to be even > more problematic. > This is because alsa assumes a fixed relationship between samplerate and > data rate, and also assumes that samples fit in an integer number of bytes. > > AFAIK dealing with hardware enc/dec has been done using gstreamer plugins. > E.g. http://www.lca2010.org.nz/slides/50315.pdf > > > Given that audioscience makes cards that support mp3 encode/decode as > well as pcm, I'd like it if alsa *did* support compressed audio... > >> Which source file can I find an example? >> >> Thanks >> Patrick >> > > regards > -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.