...

The shared memory buffer shall be split into two regions for each playback session, one for a video stream, and the other for audio (only one concurrent audio track supported, for audio track selection previous audio must be removed first). Each region must be big enough to accommodate the largest possible frame of audio/video data plus associated decryption parameters and metadata. At the end there is also a separate section for webaudio regions (common for all playback sessions). The buffer shall initially be sized to 8Mb per playback session to allow some overhead + 10kB * number of webaudio regions. There can be 0 or more Web Audio regions per Rialto Client.

For apps that can support more than one concurrent playback the shared memory buffer shall be sized accordingly and partitioned into different logical areas for each playback session. The partitions need not necessarily be equally sized, for example if an app supports one UHD and one HD playback the 'HD' partition may be smaller. There can be a maximum of one Web Audio region per Rialto Client.

draw.io Diagram

width

border	true
diagramName	Shared memory partitioning for multiple playbacks
simpleViewer	false
links	auto
tbstyle	top
lbox	true
diagramWidth	11411261
revision	12

Note that the application is not directly aware of the layout of the shared memory region or even its existence, this is all managed internally by Rialto.

...

draw.io Diagram

width

border	true
diagramName	Shared memory buffer layout for AV stream
simpleViewer	false
links	auto
tbstyle	top
lbox	true
diagramWidth	791
revision	1

...

draw.io Diagram

width

border	true
diagramName	Metadata format v1
simpleViewer	false
links	auto
tbstyle	top
lbox	true
diagramWidth	431
revision	1

...

Parameter	Size
Shared memory buffer	8Mb * max_playback_sessions + 10kb * max_web_audio_playback_sessions
Max frames to request	[24]
Metadata size per frame	Clear: Variable but <100 bytes Encrypted: TODO
Video frame region size	7Mb
Max video frame size	TODO
Audio frame region size	1Mb
Max audio frame size	TODO
Web Audio region size	10kb

...

draw.io Diagram

border	true

diagramName	Shared memory buffer layout v2
simpleViewer	false
width
links	auto
tbstyle	top
lbox	true
diagramWidth	1462
revision	13

V2 metadata uses protobuf to serialise the frames' properties to the shared memory buffer. This use of protobuf aligns with the IPC protocol but also allows support for optional fields and for fields to be added and removed without causing backward/forward compatibility issues. It also supports variable length fields so the MKS ID, IV & sub-sample information can all be directly encoded in the metadata, avoiding the complexities of interleaving them with the media frames and referencing them with offsets/lengths as used in the V1 metadata format.

enum SegmentAlignment {

  ALIGNMENT_UNDEFINED = 0;
  ALIGNMENT_NAL       = 1;
  ALIGNMENT_AU        = 2;
}
message

enum

MediaSegmentMetadata

CipherMode {

  CIPHER_MODE_UNDEFINED =

required uint32

0;
  CIPHER_MODE_CENC      = 1;  /* AES-CTR scheme

*/
  CIPHER_MODE_CBC1      =

length

2;  /* AES-CBC scheme */
  CIPHER_MODE_CENS      = 3;  /* AES-CTR subsample pattern encryption scheme */
  CIPHER_MODE_CBCS      = 4;  /* AES-CBC subsample pattern encryption scheme */
}


message MediaSegmentMetadata {

    optional uint32        = 1;             /* Number of bytes in sample */    required sint64          length       time_position        = 21;             /* PositionNumber inof streambytes in nanosecondssample */

    optional sint64 required sint64               time_position  sample_duration      = 32;             /* Frame/sample durationPosition in stream in nanoseconds */

    optional sint64                 sample_duration      = 3;             /* Frame/sample duration in nanoseconds */

   required optional uint32                 stream_id            = 4;             /* stream id (unique ID for ES, as defined in attachSource()) */

    optional uint32                 sample_rate          = 5;             /* Samples per second for audio segments */

    optional uint32                 channels_num         = 6;             /* Number of channels for audio segments */

    optional uint32                 width                = 7;             /* Frame width in pixels for video segments */

    optional uint32                 height               = 8;             /* Frame height in pixels for video segments */

    optional SegmentAlignment       segment_alignment    = 9;             /* Segment alignment can be specified for H264/H265, will use NAL if not set */

    optional bytes                  extra_data           = 10;            /* bufferBuffer containing extradata */

    optional bytes                  media_key_session_id = 11;            /* Buffer containing key session ID to use for decryption */

    optional bytes                  key_id               = 12;            /* Buffer containing Key ID to use for decryption */

    optional bytes                  init_vector          = 13;            /* Buffer containing the initialization vector for decryption */

    optional uint32                 init_with_last_15    = 14;            /* initWithLast15 value for decryption */

    optional repeated SubsamplePair sub_sample_info      = 15;            /* If present, use gather/scatter decryption based on this list of clear/encrypted byte lengths. */

                                                                          /* If not present and content is encrypted then entire media segment needs decryption. (unless    */

*/

message SubsamplePair

{

    required uint32_t               num_clear_bytes      = 1;             /* How many of next bytes in sequence are clear */    required uint32_t            /* cipher_mode  num_encrypted_bytes  = 2;indicates pattern encryption in which case crypt/skip byte block value specify    */

                                                                          /* How many of next bytes in sequence are encrypted */

}

Playback Control

the encryption pattern)                                                                       */

    optional bytes                  codec_data           = 16;            /* Buffer containing updated codec data for video segments */

    optional CipherMode             cipher_mode          = 17;            /* Block cipher mode of operation when common encryption used */

    optional uint32                 crypt_byte_block     = 18;            /* Crypt byte block value for CBCS cipher mode pattern */

    optional uint32                 skip_byte_block      = 19;            /* Skip byte block value for CBCS cipher mode pattern */
    optional Fraction               frame_rate           = 20;            /* Fractional frame rate of the video segments */

message SubsamplePair

{

    optional uint32_t               num_clear_bytes      = 1;             /* How many of next bytes in sequence are clear */

    optional uint32_t               num_encrypted_bytes  = 2;             /* How many of next bytes in sequence are encrypted */

}

Playback Control

Rialto Rialto interactions with Client & GStreamer

...

PlantUML Macro

format	SVG
title	Render Frame

@startuml

autonumber

box "Container" #LightGreen
participant Netflix
participant DPI
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
end box

Netflix            ->  DPI:              renderFrame()
DPI                ->  rialtoClient:     renderFrame()
rialtoClient       ->  rialtoServer:     renderFrame()
opt Frame renderable
rialtoServer       ->  GStreamer_server: Trigger rendering of frame

opt Frame rendered successfully

note across: It is a Netflix requirement to call updatePlaybackPosition() after renderFrame()
rialtoServer       -->  rialtoClient:     notifyPositionrenderFrame(position)
rialtoClient       -->  DPIrialtoServer:     renderFrame()
opt Frame renderable
rialtoServer       notifyPosition(position)
DPI->  GStreamer_server: Trigger rendering     of frame
rialtoServer       --> NetflixrialtoClient:     status=true
else renderFrame() called in bad updatePlaybackPosition(pts)
state
rialtoServer       --> rialtoClient:     status=truefalse
end
else
rialtoServerrialtoClient       --> rialtoClientDPI:              status=false
end

else renderFrame() called in bad state
rialtoServer
DPI                --> Netflix:           --> rialtoClient:     status=false
end

rialtoClientstatus

@enduml

Media data pipeline

Note that the data pipelines for different data sources (e.g. audio & video) should operate entirely independently. Rialto should

attempt to keep the shm buffer as full as possible by requesting a refill for that source whenever the source's memory buffer is empty
attempt to push all available frames for a source to GStreamer, i.e. push until Gstreamer indicates that it can accept no more data

Cobalt to Gstreamer

PlantUML Macro

format	SVG
title	Cobalt pushing media frames

@startuml

autonumber

box "Container" #LightGreen
participant Cobalt
participant Starboard
participant GStreamer_client_appsrc
participant decrypter_element
participant ocdmProxy
end box


Cobalt       --> DPI:              status
DPI  ->      Starboard:        --> Netflix:          status

@enduml

Media data pipeline

Note that the data pipelines for different data sources (e.g. audio & video) should operate entirely independently. Rialto should

attempt to keep the shm buffer as full as possible by requesting a refill for that source whenever the source's memory buffer is empty
attempt to push all available frames for a source to GStreamer, i.e. push until Gstreamer indicates that it can accept no more data

Cobalt to Gstreamer

PlantUML Macro

format	SVG
title	Cobalt pushing media frames

@startuml

autonumber

box "Container" #LightGreen
participant Cobalt
participant Starboard
participant GStreamer_client_appsrc
participant GStreamer_client_rialto_sink
participant ocdmProxy
end box


Cobalt SbPlayerWriteSample2(player, sample[])
note right: Currently sample array size must be 1
Starboard                     ->  Starboard:                    Create GstBuffer and add media data from sample  ->  Starboard:to it

opt Sample encrypted
Starboard                     SbPlayerWriteSample2(player, sample[])
note right: Currently sample array size must be 1->  GStreamer_client_appsrc:      gst_buffer_add_protection_meta(gst_buffer, decrytion_params)
end


Starboard                     ->  StarboardGStreamer_client_appsrc:      gst_app_src_push_buffer(app_src, gst_buffer)
GStreamer_client_appsrc             Create GstBuffer and add media data from sample to it

opt Sample encrypted
Starboard--> decrypter_element:            data flows through client pipeline
decrypter_element              ->  GStreamer_client_appsrc: decrypter_element:            gst_buffer_addget_protection_meta(gst_buffer, decrytion_params)
end


Starboard
opt Implementation before CBCS support added
decrypter_element             ->  ocdmProxy:            ->  GStreamer_client_appsrc:      gstopencdm_gstreamer_appsession_srcdecrypt_push_buffer(app_src, gst_buffer)
GStreamer_client_appsrcex(key_session, buffer, sub_samples, iv, kid, init_with_last_15, caps)
ocdmProxy        --> GStreamer_client_rialto_sink: data flows through client pipeline
GStreamer_client_rialto_sink  ->  GStreamer_client_rialto_sink: gst_buffer_get_protection_meta(buffer)
GStreamer_client_rialto_sink  ->  ocdmProxy:                    Create gst struct  opencdm_gstreamer_session_decrypt(key_session, buffer,containing encryption data decrytion_params)
ocdmProxy  
else Implementation after CBCS support added
decrypter_element             ->  ocdmProxy:     ->  ocdmProxy:             opencdm_gstreamer_session_decrypt_buffer(key_session, buffer, caps)
end

ocdmProxy     Create gst struct containing encryption data decrytion_params
ocdmProxy          ->  decrypter_element:          ->  GStreamer_client_rialto_sink: gst_buffer_add_protection_meta(buffer, metadata)
note left
Decryption is deferred until the data is sent to Rialto so
attach the required decryption parameters to the media frame
which are then ready to be passed to Rialto when it requests
more data.
end note

@enduml

...

PlantUML Macro

format	SVG
title	Pushing data to Gstreamer server pipeline

@startuml

autonumber

box "Platform" #LightGreen
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
participant Ocdm
end box

note across
Gstreamer app source uses 2 signals, need-data and enough-data,
to notify its client whether it needs more data. Rialto server
should only push data when the appsrc indicates that it is in
the need-data state.
end note


loop While appsrc needs data && appsrc data available in shm buffer

rialtoServer       ->  rialtoServer:      Extract frame's metadata from shm
opt Frame encrypted

rialtoServer	   ->  GStreamer_server:  gst_buffer_add_protection_meta(buffer, meta)

end

rialtoServer       ->  GStreamer_server:  Set width/height caps
opt new codec_data Extractin frame's
rialtoServer metadata from shm
opt Frame encrypted

rialtoServer	   ->   GStreamerGStreamer_server:  gst_buffer_add_protection_meta(buffer, meta)
Set codec_data caps
end

rialtoServer       ->  GStreamer_server:  gst_app_src_push_buffer(src, gst_buffer)
rialtoServer       ->  rialtoServer:      'Remove' frame from shm

opt First video frame pushed at start of playback / after seek
note across: Not currently implemented
rialtoServer       --/ rialtoClient:      notifyFrameReady(frame_timestamp)
end

opt Appsrc data exhausted from shm
opt (status == EOS) for this appsrc
rialtoServer       ->  GStreamer_server:      notify EOS
else Not EOS
rialtoServer       --/ rialtoClient:      notifyNeedMediaData(...)
end
end

end

@enduml

...

PlantUML Macro

format	SVG
title	Decrypt Frames on Gstreamer server pipeline

@startuml

autonumber

box "Platform" #LightGreen
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
participant Ocdm
end box

GstreamerGStreamer_server   ->  rialtoServer:      decrypt(buffer)

rialtoServer	   ->  GStreamer_server:  gst_buffer_get_protection_meta(buffer)
 
opt Protection Meta exists (Frame encrypted)
 
rialtoServer       ->  rialtoServer:      Extract frame's metadata

opt media_keys.key_system == "com.netflix.playready"
rialtoServer       ->  Ocdm:              opencdm_select_key_id(ocdm_session, kid)
end


opt Implementation before CBCS support added
rialtoServer       ->  Ocdm:              opencdm_gstreamer_session_decrypt_ex(ocdm_session, gst_buffer, subsample_info, iv, key, init_with_last_15)
end _last_15, caps)
else Implementation after CBCS support added
rialtoServer       ->  Ocdm:              opencdm_gstreamer_session_decrypt_buffer(ocdm_session, gst_buffer, caps)
end

end

@enduml

Playback State

Position Reporting

...

PlantUML Macro

format	SVG
title	Underflow

@startuml

autonumber

box "Container" #LightGreen
participant Cobalt
participant Starboard
participant GStreamer_client
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server
end box

== Initialisation - register for callbacks ==

opt Video source attached
rialtoServer       ->  GStreamer_server:     g_signal_connect(video_decoder, getVideoUnderflowSignalName_soc(), video_underflow_cb, user_data);
GStreamer_server   --> rialtoServer:         video_handler_id
end

opt Audio source attached
rialtoServer       ->  GStreamer_server:     g_signal_connect(audio_decoder, getAudioUnderflowSignalName_soc(), audio_underflow_cb, user_data);
GStreamer_server   --> rialtoServer:         audio_handler_id
end


== Termination - unregister for callbacks ==

opt Video source removed
rialtoServer       ->  GStreamer_server:     g_signal_handler_disconnect(video_decoder, video_handler_id);
GStreamer_server   --> rialtoServer:
end

opt Audio source removed
rialtoServer       -> GStreamer_server:     g_signal_handler_disconnect(audio_decoder, audio_handler_id);
GStreamer_server   --> rialtoServer:
end


== Underflow ==

opt Data starvation in server AV pipeline
GStreamer_server   -/  rialtoServer:         video_underflow_cb() or audio_underflow_cb()
rialtoServer       ->  rialtoServer:         Set pipeline state to paused
rialtoServer       -/  rialtoClient:         notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PAUSED)
rialtoClient       -/  GStreamer_client:     notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PAUSED)
rialtoServer       -/  rialtoClient:         notifyNetworkState(pipeline_session, NETWORK_STATE_STALLED)
rialtoClient       -/  GStreamer_client:     notifyNetworkState(pipeline_session, NETWORK_STATE_STALLED)

note over Starboard, GStreamer_client
Starboard does not have any support for underflow
so the event can be ignored for this integration.
end note

note across
There will be one ore more pending need data requests at this point which if serviced will allow playback to resume
end note

end

== Recovery ==

opt rialtoServer detects that any need media data requests pending at point of underflow are now serviced and pushed to GStreamer_server || EOS signalled for any underflowed sources
note across
It is likely that underflow is due to one source becoming starved whilst data is buffered for other sources, so waiting until pending request(s) are serviced should allow playback to resume.
There are also some YT conformance tests that delay signalling EOS for an underflowed source whilst the other continues to stream hence the EOS condition to allow streaming to resume for the valid source.
end note

rialtoServer       ->  rialtoServer:         Set pipeline state to playing
rialtoServer       -/  rialtoClient:         notifyNetworkState(pipeline_session, NETWORK_STATE_BUFFEREDnote across
underflow_enabled: Underflow is enabled when we're in playing state and source is attached.
underflow_cancelled: Underflow may be cancelled when haveData is called between notification from GStreamer and Underflow task handling.
end note
opt underflow_enabled && !underflow_cancelled
rialtoServer       -/  rialtoClient:         notifyBufferUnderflow(source_id)
rialtoClient       -/  GStreamer_client:     notifyBufferUnderflow(source_id)
GStreamer_client   -/  Starboard:            emit video_underflow_cb() or audio_underflow_cb()

note over Starboard, GStreamer_client
Starboard does not have any support for underflow
so the event can be ignored for this integration.
end note

end

note across
There will be one re more pending need data requests at this point which if serviced will allow playback to resume
end note

end

@enduml

Non-fatal Playback Failures

Decryption: Any encrypted frames that fail to decrypt are dropped, and an error notification is propagated to the rialto-gstreamer, at which point a decryption error is raised on the sink.

PlantUML Macro

format	SVG
title	Non-fatal Errors

@startuml

autonumber

box "Container" #LightGreen
participant Application
participant rialtoGstreamer
participant rialtoClient
end box

box "Platform" #LightBlue
participant rialtoServer
participant GStreamer_server 
end box

== Decryption ==
GStreamer_server   ->  rialtoServer:      decrypt(buffer)

rialtoServer	   ->  GStreamer_server:  MediaKeyErrorStatus::Fail
GStreamer_server   ->  GStreamer_server:  GST_BASE_TRANSFORM_FLOW_DROPPED 

note over GStreamer_server
Frame is dropped but playback is unaffected.
end note 

GStreamer_server   ->  rialtoServer:      GST_MESSAGE_WARNING(src, GST_STREAM_ERROR_DECRYPT)

rialtoServer       -/  rialtoClient:      notifyPlaybackError(MediaSourceType, PlaybackError::DECRYPTION)
rialtoClient       -/  GStreamer_client rialtoGstreamer:     notifyNetworkState(pipeline_session, NETWORK_STATE_BUFFERED)
rialtoServer       -/  rialtoClient:         notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PLAYING)
rialtoClient       -/  GStreamer_client:     notifyPlaybackState(pipeline_session, PLAYBACK_STATE_PLAYING)

endnotifyPlaybackError(MediaSourceType, PlaybackError::DECRYPTION)
 
note over rialtoGstreamer
Posting an error message on the sink make the\n
sink unable to continue playing back content.
end note   
rialtoGstreamer    -/  Application:       GST_MESSAGE_ERROR(sink, GST_STREAM_ERROR_DECRYPT)

@enduml

RDK Resources

[RDK Preferred]

Code Management Facility

RDK Forums

[RDK Conferences]

RDK Support

Archives

Versions Compared

Old Version 6

New Version Current

Key

Playback Control

Playback Control

Rialto Rialto interactions with Client & GStreamer

Media data pipeline

Cobalt to Gstreamer

Media data pipeline

Cobalt to Gstreamer

Playback State

Position Reporting

Non-fatal Playback Failures

RDK Resources

[*RDK Preferred*]

Code Management Facility

RDK Forums

[RDK Conferences]

RDK Support

Archives

Page History

Versions Compared

Old Version 6

New Version Current

Key

Playback Control

Playback Control

Rialto Rialto interactions with Client & GStreamer

Media data pipeline

Cobalt to Gstreamer

Media data pipeline

Cobalt to Gstreamer

Playback State

Position Reporting

Non-fatal Playback Failures

[RDK Preferred]