Av:Developer:Scd - Revision history

Simonc: /* Overview */

2019-12-13T10:08:34Z

Overview

← Older revision		Revision as of 10:08, 13 December 2019
Line 6:		Line 6:
	* There is a constant TCP connection between sender and receiver, avoiding the need for application-level resend support		* There is a constant TCP connection between sender and receiver, avoiding the need for application-level resend support
	* It uses the clock of the receiver, allowing for higher quality playback if the sender is on a desktop computer		* It uses the clock of the receiver, allowing for higher quality playback if the sender is on a desktop computer
-	* It offers the receiver limited control over the stream – initially ~~seeking within a track or skipping between tracks~~. While the primary control UI may reside on the sender device, this allows for integration with any Ir handset for the receiver.	+	* It offers the receiver limited control over the stream – initially Transport (play / pause / stop) and Volume. While the primary control UI may reside on the sender device, this allows for basic integration with any Ir handset for the receiver.

	== Sample Code ==		== Sample Code ==

Simonc: FormatDsd

2018-02-21T14:25:33Z

FormatDsd

← Older revision		Revision as of 14:25, 21 February 2018
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	\|-		\|-
	\| Format		\| Format
-	\| Format for the following audio. Must be sent before any audio.	+	\| Format for the following (PCM) audio. Must be sent before any audio.
		+	\| Sender
		+	\|-
		+	\| FormatDsd
		+	\| Format for the following (DSD) audio. Must be sent before any audio.
	\| Sender		\| Sender
	\|-		\|-
Line 115:		Line 119:
	* 2 - MetaDataOh		* 2 - MetaDataOh
	* 3 – Format		* 3 – Format
		+	* 4 – FormatDsd
	* 5 – Audio		* 5 – Audio
	* 7 – MetatextDidl		* 7 – MetatextDidl
Line 225:		Line 230:
	* Bit 1 - Lossless		* Bit 1 - Lossless
	* Bit 2 - Live (content generated upstream of the Sender, e.g. internet radio)		* Bit 2 - Live (content generated upstream of the Sender, e.g. internet radio)
		+	* Bit 3 - Broadcastable (whether the Receiver is allowed to offer the following audio via any multi-room protocols
		+	* Bits 4-7 - Reserved. Must be zero.
		+	\|-
		+	\| 1
		+	\| CodecNameLength
		+	\| Length, in bytes, of the codec name
		+	\|-
		+	\| r
		+	\| CodecName
		+	\| The codec name, where r = CodecNameLength
		+	\|-
		+	\| '''FormatDsd'''
		+	\|
		+	\|
		+	\|-
		+	\| 4
		+	\| SampleRate
		+	\| Sample rate of the following audio
		+	\|-
		+	\| 1
		+	\| Channels
		+	\| Number of channels of the following audio
		+	\|-
		+	\| 2
		+	\| SampleBlockBits
		+	\| Block size (in bits) of DSD data. 2 for stereo where left/right channels are interleaved, 16 for stereo with one byte of left subsamples followed by one byte of right subsamples, etc.
		+	\|-
		+	\| 8
		+	\| SampleStart
		+	\| Sample position of the first sample in the next <tt>Audio</tt> message
		+	\|-
		+	\| 8
		+	\| SamplesTotal
		+	\| Total number of samples in the following audio (requirement for this to be confirmed)
		+	\|-
		+	\| 1
		+	\| Flags
		+	\|
		+	* Bit 0 - Seekable
		+	* Bit 1-2 - Reserved. Must be zero.
	* Bit 3 - Broadcastable (whether the Receiver is allowed to offer the following audio via any multi-room protocols		* Bit 3 - Broadcastable (whether the Receiver is allowed to offer the following audio via any multi-room protocols
	* Bits 4-7 - Reserved. Must be zero.		* Bits 4-7 - Reserved. Must be zero.

Simonc: /* Protocol */

2018-01-04T09:27:14Z

Protocol

← Older revision		Revision as of 09:27, 4 January 2018
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	\| BitRate		\| BitRate
	\| Bit rate of the following audio		\| Bit rate of the following audio
-	\|-
-	~~\| 8~~
-	~~\| SamplesTotal~~
-	~~\| Total number of samples in the following audio (requirement for this to be confirmed)~~
	\|-		\|-
	\| 8		\| 8
	\| SampleStart		\| SampleStart
	\| Sample position of the first sample in the next <tt>Audio</tt> message		\| Sample position of the first sample in the next <tt>Audio</tt> message
		+	\|-
		+	\| 8
		+	\| SamplesTotal
		+	\| Total number of samples in the following audio (requirement for this to be confirmed)
	\|-		\|-
	\| 1		\| 1

Simonc: /* Protocol */

2017-12-22T10:51:56Z

Protocol

← Older revision		Revision as of 10:51, 22 December 2017
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	\|-		\|-
	\| MetatextOh		\| MetatextOh
-	\| Metadata relevant to a portion of a track.<br>May be sent [0..n] times during a track.<br>Uses [[Av::OhMetadata \| OpenHome Metadata format]].	+	\| Metadata relevant to a portion of a track.<br>May be sent [0..n] times during a track.<br>Uses [[Av::OhMetadata \| OpenHome Metadata format]]. Note that a uri does not need to be specified.
	\| Sender		\| Sender
	\|-		\|-

Simonc: /* Protocol */

2017-06-26T08:15:47Z

Protocol

← Older revision		Revision as of 08:15, 26 June 2017
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	\| Audio data. Where s = NumSamples * (BitDepth/8) * NumChannels.<br>Multi-channel audio must supply data sample at a time, with left channel first. Audio is packed (i.e. no padding bytes rounding samples up to 32-bit boundaries) and big endian.		\| Audio data. Where s = NumSamples * (BitDepth/8) * NumChannels.<br>Multi-channel audio must supply data sample at a time, with left channel first. Audio is packed (i.e. no padding bytes rounding samples up to 32-bit boundaries) and big endian.
	\|-		\|-
-	\| '''~~Metatextdidl~~'''	+	\| '''MetatextDidl'''
	\|		\|
	\|		\|

Simonc: /* Sample Code */

2017-06-23T14:13:29Z

Sample Code

← Older revision		Revision as of 14:13, 23 June 2017
Line 9:		Line 9:

	== Sample Code ==		== Sample Code ==
-	~~Sample~~ code ~~exists for all key aspects~~ of the Sender ~~– server~~, ~~framing~~ and control.	+	[https://github.com/openhome/ohPipeline/tree/master/OpenHome/Av/Scd ohPipeline] contains sample code.
		+
		+	<tt>WavSender</tt> contains an example of a trivial SCD Sender, scanning a single directory and decoding then sending any WAV files it finds. (Note that compilation of this is currently disabled. <tt>DirScanner::Run()</tt> contains code from an experimental precursor to C++17's <tt>std::filesystem::directory_iterator</tt>. Current code is compatible with VS2013; it should only require a couple of lines of change to make this compile against any more recent compiler.)
		+
		+	Code in the [https://github.com/openhome/ohPipeline/tree/master/OpenHome/Av/Scd Scd] and [https://github.com/openhome/ohPipeline/tree/master/OpenHome/Av/Scd/Sender Sender] directories should be usable without any change. It will be possible to write a commercial quality sender using the <tt>ScdSender</tt> library, passing audio into <tt>IScdSupply</tt> and relying on the configuration of <tt>ScdMsgFactory</tt> to determine how much audio is buffered by the Sender.
		+
		+	Sample code demonstrating how a Sender can control a Receiver via ODP is coming soon. For now, see [https://github.com/openhome/ohPipeline/blob/master/OpenHome/Net/Odp/Tests/TestDvOdp.cpp ODP tests] for a basic example.

	== Discovery ==		== Discovery ==

Simonc: /* SSDP */

2017-06-23T13:49:44Z

SSDP

← Older revision		Revision as of 13:49, 23 June 2017
Line 16:		Line 16:
	* Check <tt>Attributes</tt> on <tt>Product</tt> service for <tt>"Transport"</tt>		* Check <tt>Attributes</tt> on <tt>Product</tt> service for <tt>"Transport"</tt>
	* Check <tt>Modes</tt> on <tt>Transport</tt> service for <tt>"scd"</tt>		* Check <tt>Modes</tt> on <tt>Transport</tt> service for <tt>"scd"</tt>
		+	or
		+	* Check <tt>SourceXml</tt> on <tt>Product</tt> for a source with <tt>Type</tt> of <tt>"scd"</tt>
		+
	=== mDNS ===		=== mDNS ===
	Search for <tt>_openhome._odp</tt> service to identify ODP endpoint		Search for <tt>_openhome._odp</tt> service to identify ODP endpoint

Simonc at 13:48, 23 June 2017

2017-06-23T13:48:21Z

← Older revision		Revision as of 13:48, 23 June 2017
Line 91:		Line 91:
	! '''Description'''		! '''Description'''
	\|-		\|-
-	\| '''Header ~~(all messages)~~'''	+	\| '''Header'''
		+	\|
		+	\| Prefixes to all messages below
	\|-		\|-
	\| 4		\| 4

Simonc: Add wire protocol

2017-06-23T13:47:07Z

Add wire protocol

Show changes

Simonc: Created page with "= Songcast Direct = == Overview == Songcast Direct (SCD) can be used to send decoded audio from any computing device to an OpenHome device. The Sender device is responsible for ..."

2017-06-23T12:47:35Z

Created page with "= Songcast Direct = == Overview == Songcast Direct (SCD) can be used to send decoded audio from any computing device to an OpenHome device. The Sender device is responsible for ..."

New page

= Songcast Direct =
== Overview ==
Songcast Direct (SCD) can be used to send decoded audio from any computing device to an OpenHome device. The Sender device is responsible for decoding audio to PCM, framing this in a simple protocol and making it available via a simple TCP server. The Receiver pulls data from this server, giving the Receiver complete control of the audio clock.

A Songcast Direct sender performs a broadly similar role to a Songcast sender. Applications that perform their own decoding to PCM will find SCD is easier to integrate and offers higher audio performance:
* There is a constant TCP connection between sender and receiver, avoiding the need for application-level resend support
* It uses the clock of the receiver, allowing for higher quality playback if the sender is on a desktop computer
* It offers the receiver limited control over the stream – initially seeking within a track or skipping between tracks. While the primary control UI may reside on the sender device, this allows for integration with any Ir handset for the receiver.

== Sample Code ==
Sample code exists for all key aspects of the Sender – server, framing and control.

== Discovery ==
=== SSDP ===
First search for <tt>av-openhome-org:service:Product:2</tt> then either
* Check <tt>Attributes</tt> on <tt>Product</tt> service for <tt>"Transport"</tt>
* Check <tt>Modes</tt> on <tt>Transport</tt> service for <tt>"scd"</tt>
=== mDNS ===
Search for <tt>_openhome._odp</tt> service to identify ODP endpoint

== Control ==
Control of the Receiver is out of band, via the standard [[OhMediaDevelopers#Network_Services | OpenHome network APIs]]. These are available over UPnP or [[OhMediaDevelopers#ODP | ODP]] (a single connected socket).

== Protocol ==
The protocol used for communication between Sender and Receiver contains the following message types:
{|
! '''Type'''
! '''Description'''
! '''Sent by'''
|-
| Ready
| Signals availability and version support to other party
| Receiver & Sender
|-
| MetadataDidl
| Metadata relevant until the end of the next track. Will cause the receiver to reset its reported time indicator for the audio stream. Should be sent after all Audio for any preceding track. Uses DIDL-Lite.
| Sender
|-
| MetadataOh
| Metadata relevant until the end of the next track. Will cause the receiver to reset its reported time indicator for the audio stream. Should be sent after all Audio for any preceding track. Uses [[Av::OhMetadata | OpenHome Metadata format]].
| Sender
|-
| Format
| Format for the following audio. Must be sent before any audio.
| Sender
|-
| Audio
| Decoded audio. Can only be sent after a <tt>Format</tt> message describing its sample rate etc.
| Sender
|-
| MetatextDidl
| Metadata relevant to a portion of a track. May be sent [0..n] times during a track. Uses DIDL-Lite.
| Sender
|-
| MetatextOh
| Metadata relevant to a portion of a track. May be sent [0..n] times during a track. Uses [[Av::OhMetadata | OpenHome Metadata format]].
| Sender
|-
| Halt
| Indicates that a break in audio follows. E.g. at the end of a track with no further tracks to be played, or when the Sender has paused.
| Sender
|-
| Disconnect
| Indicates that the originator of the message is closing its SCD session. No further audio will be available. The message receiver should disconnect its socket.
| Receiver & Sender
|-
| Seek
| Indicates that the Receiver wants to jump to a different point in the current track. Is only sent for tracks that the Sender has indicated support seeking.
| Receiver
|-
| Skip
| Indicates that the Receiver wants to immediately jump to the next or previous track.
| Receiver
|}