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- Bartosz: we can get raw streams (unmixed streams) by bipassing the Android framework mixer.
- Applications can request for this, but by defaults all internal streams are going through the framework mixer.
- There is also the Android Audio API which is used for low latency streams that allows us to get raw streams.
- Gunnar:Unknown User (bartoszbialek) please add your comments in the page Android and System Level Audio
- Suhasini: what about the Network audio devices? can we use the device outbus for direct access of raw streams?
- Piotr: in summary, this API is used to handle addressable ports not for use of raw streams
- Bartosz: this is used for Android to capture external streams and represent them as internal streams but the audio path is longer (more latency)
- Raw Streams are both input and output streams
- Gunnar: when we talk about Raw streams do we want to take into consideration compressed streams
- Wassim: this is a link for the data format https://source.android.com/devices/audio/data_formats
- Piotr: the PCM format is mostly used and since we are starting with a generic solution, might as well not extend it beyond this scope
- Gunnar: what about the encoded and compressed streams?
- Piotr: multimedia framework is doing this and it's not part of the Audio HAL
- Bartosz: Android controls whether we want to take the stream and decoded using the CPU or not (this is called Offloading)
- Wassim: each stream has properties: depth, container size, compression, etc.
- here is a page of more attribute
- gunnar: Unknown User (wassim.filali) : please write down the decision about supporing the comrpession in our scope in the page Android and System Level Audio
- Wassim : As described in the Android data_formats page, Compression is a Property of each audio stream. Although audio streams are most of the time uncompressed (PCM) due to avoidance of compression decompression cpu time loss, it might happens that a source stream is provided compressed by default. In that case the common formats are FLAC (lossless) and MP3, AAC (lossy). Further details about compression would be case specific.
Input streams
- Gunnar: input streams no one yet investigated
- Gunnar: Unknown User (niskandar): investigate input steams as well from the page Android and System Level Audio
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- Unknown User (bartoszbialek) please add your comments in the page Android and System Level Audio
- Unknown User (wassim.filali) : please write down the decision about supporing the comrpession
- Unknown User (niskandar): investigate input steams as well from the page Android and System Level Audio
- Piotr Krawczyk : please update the presentation attached
- Gunnar Andersson: provide a place to add the code of the POC
- @All: please check the topics of investigation to see if you would like to add more topics to the page Android and System Level Audio
- @All check your emails to see if you have received the invitation about the summit
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