Motown: Use new TimelineTransform and related definitions

mojo/services/media/common/interfaces/rate_control.mojom

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-[DartPackage="mojo_services"]
-module mojo.media;
-
-// TimelineQuad
-// TODO(dalesat): Rename reference -> presentation.
-// TODO(dalesat): Rename target -> reference.
-//
-// A structure which holds the four numbers needed to define a linear
-// relationship between the points in two different timelines.  The relationship
-// is expressed using 4 integers in order to facilitate compositions of multiple
-// transformations (A->B can be composed with B->C to produce the transformation
-// from A->C), and to minimize rounding and scaling errors when mapping points
-// between timelines which do not have an integer scaling relationship between
-// each other.
-//
-// These values are used to define the following functions which map from
-// points from the reference timeline to the target timeline, and back again.
-//
-// Let r be a point in the reference timeline.
-// Let t be a point in the target timeline timeline.
-// Let ref and tgt be abbreviations for reference and target in equations below.
-//
-// Given that r and t represent the same instant in time (in a single frame of
-// reference)
-//
-// t = f(r) = (((r - ref_offset) * tgt_delta) / ref_delta) + tgt_offset
-// r = F(t) = (((t - tgt_offset) * ref_delta) / tgt_delta) + ref_offset
-//
-// See also...
-// mojo/services/media/common/linear_transform.h
-//
-// no-format
-struct TimelineQuad {
-  int64  reference_offset = 0;
-  int64  target_offset    = 0;
-  uint32 reference_delta  = 0;
-  uint32 target_delta     = 1;
-};
-// end-no-format
-
-// TimelineTransform
-// TODO(dalesat): Rename reference -> presentation.
-// TODO(dalesat): Rename target -> reference.
-//
-// A structure which holds both a timeline quad, and a pair of identifiers which
-// define the specific timelines which are the reference and target timelines.
-struct TimelineTransform {
-  // TODO: These constants should probably defined by a central time management
-  // service, not here.
-  const uint32 kLocalTimeID = 0xFFFFFFFF;
-  const uint32 kContextual = 0xFFFFFFFE;
-
-  TimelineQuad quad;
-  uint32 reference_timeline_id = kContextual;
-  uint32 target_timeline_id = kLocalTimeID;
-};
-
-// RateControl
-//
-// An interface typically exposed by media renderers which allow producers of
-// media to specify how the presentation time stamps of the media queued to the
-// renderer relate to real time.  Users may initialize the transformation with a
-// specific Quad, change the rate immediately in a first order contiguous
-// fashion, or schedule ranges in the rate at points in time on either the
-// reference or target timelines.
-interface RateControl {
-  // Get the current quad which describes the transformation between the
-  // reference and target timelines.
-  GetCurrentTransform() => (TimelineTransform trans);
-
-  // Immediately, explicitly set the quad which describes the mapping from
-  // reference to target timeline.  It is understood that this can cause
-  // discontinuities and should only be used in situations which are already
-  // fundamentally discontinuous (startup/seeking, for example)
-  SetCurrentQuad(TimelineQuad quad);
-
-  // Configure the target timeline ID.  Note, the reference timeline ID will
-  // always be contextual.
-  SetTargetTimelineID(uint32 id);
-
-  // Immediately change the rate of the existing transformation in a fashion
-  // which is first order continuous with the current transformation.
-  SetRate(uint32 reference_delta, uint32 target_delta);
-
-  // Schedule a first order continuous rate change at the specified reference
-  // time.
-  SetRateAtReferenceTime(uint32 reference_delta,
-                         uint32 target_delta,
-                         int64 reference_time);
-
-  // Schedule a first order continuous rate change at the specified target time.
-  SetRateAtTargetTime(uint32 reference_delta,
-                      uint32 target_delta,
-                      int64 target_time);
-
-  // Cancel any pending rate changes
-  CancelPendingChanges();
-};