sdk/fidl/fuchsia.audio/stream_sink.fidl

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.audio;

using fuchsia.drm;
using fuchsia.media2;
using zx;

/// A packet sink for cross-process audio stream transport, implemented by audio consumers and used
/// by audio producers.
protocol StreamSink {
    /// Puts a packet to the sink.
    PutPacket(resource table {
        /// Describes the packet. This field is required.
        1: packet Packet;

        /// Eventpair closed when the consumer is done with the packet and the buffer region
        /// associated with the packet may be reused. Packets may be released in any order. The
        /// release fence may be duplicated by the service, so it must be sent with right
        /// `ZX_RIGHT_DUPLICATE`. This field is optional.
        2: release_fence zx.handle:EVENTPAIR;
    });

    /// Starts a new segment. Packets following this request and preceding the next such request
    /// are assigned to the segment.
    StartSegment(table {
        /// Identifies the segment. New segment IDs for a given connection must always be strictly
        /// increasing. This field is required.
        1: segment_id int64;
    });

    /// Indicates that the end of the stream has been reached. Consumers such as audio renderers
    /// signal their clients when the last packet before end-of-stream has been rendered, so the
    /// client knows when to, for example, change the UI state of a player to let the user know the
    /// content is done playing. This method is logically scoped to the current segment. A
    /// `SetSegment` request and (typically) more packets may follow this request.
    End();

    /// Sent immediately before the producer closes to indicate why the producer is closing the
    /// connection. After sending this request, the producer must refrain from sending any more
    /// messages and close the connection promptly.
    WillClose(table {
        /// Reason the connection will close.
        1: reason fuchsia.media2.ProducerClosedReason;
    });

    /// Sent immediately before the consumer closes to indicate why the consumer is closing the
    /// connection. After sending this event, the consumer must refrain from sending any more
    /// messages and close the connection promptly.
    -> OnWillClose(table {
        /// Reason the connection will close.
        1: reason fuchsia.media2.ConsumerClosedReason;
    });
};

/// Describes a packet delivered via `StreamSink`.
type Packet = table {
    /// Location of the payload for this packet. This field is required.
    1: payload fuchsia.media2.PayloadRange;

    /// Timestamp indicating when this packet should be presented. Omitting this field implies an
    /// `unspecified_best_effort` timestamp.
    2: timestamp Timestamp;

    /// Capture time for this packet as a system monotonic time value. This field is optional and
    /// may be set by capturers to indicate when this packet was captured.
    3: capture_timestamp zx.time;

    /// Flags describing the packet. Omitting this field implies all flags are clear.
    4: flags PacketFlags;

    /// Indicates how many frames should be dropped from the front of the output packet produced by
    /// a decoder from this input packet. This value should only be provided for compressed streams.
    /// If this field is omitted, no front frames should be dropped.
    5: front_frames_to_drop uint32;

    /// Indicates how many frames should be dropped from the back of the output packet produced by
    /// a decoder from this input packet. This value should only be provided for compressed streams.
    /// If this field is omitted, no back frames should be dropped.
    6: back_frames_to_drop uint32;

    /// Describes the encryption applied to this packet. Omitting this field implies the packet is
    /// not encrypted.
    7: encryption_properties fuchsia.drm.PacketEncryptionProperties;
};

/// Indicates the position of an audio packet in the stream timeline.
type Timestamp = flexible union {
    /// Specific time in the stream timeline. Units vary and are provided when the connection
    /// is established.
    1: specified int64;

    /// Indicates the packet should be presented immediately after the previous packet, if there is
    /// a previous packet. If there is no previous packet, this option is equivalent to a
    /// `specified` value of 0.
    ///
    /// This option implies that the stream timeline should not ‘slip’ even if the packet
    /// arrives late. The packet is intended to be presented immediately after the previous packet,
    /// and the resulting timing is to be maintained regardless of the arrival time of the packet.
    2: unspecified_continuous struct {};

    /// Indicates the packet should be presented as soon as possible after the previous packet, if
    /// there is one, as soon as possible if not.
    ///
    /// This option implies that the stream time should ‘slip’ if the packet arrives too late
    /// to be rendered immediately after the previous packet. This option is often used when a gap
    /// occurs in an un-timestamped stream, perhaps due to a lossy upstream source.
    3: unspecified_best_effort struct {};
};

/// Flags describing a packet.
type PacketFlags = flexible bits {
    /// Indicates that this packet is provided only so that later packets can be interpreted. A
    /// decoder should drop the decompressed packets generated from this packet.
    DROP_AFTER_DECODE = 0x01;
};