1/*
2 * Copyright (C) 2020 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.hardware.audio@7.0;
18
19/**
20 * Asynchronous stream out event callback interface. The interface provides
21 * a way for the HAL to notify platform when there are changes, e.g. codec
22 * format change, from the lower layer.
23 */
24interface IStreamOutEventCallback {
25    /**
26     * Codec format changed.
27     *
28     * onCodecFormatChanged returns an AudioMetadata object in read-only ByteString format.
29     * It represents the most recent codec format decoded by a HW audio decoder.
30     *
31     * Codec format is an optional message from HW audio decoders. It serves to
32     * notify the application about the codec format and audio objects contained
33     * within the compressed audio stream for control, informational,
34     * and display purposes.
35     *
36     * audioMetadata ByteString is convertible to an AudioMetadata object through
37     * both a C++ and a C API present in Metadata.h [1], or through a Java API present
38     * in AudioMetadata.java [2].
39     *
40     * The ByteString format is a stable format used for parcelling (marshalling) across
41     * JNI, AIDL, and HIDL interfaces.  The test for R compatibility for native marshalling
42     * is TEST(metadata_tests, compatibility_R) [3].  The test for R compatibility for JNI
43     * marshalling is android.media.cts.AudioMetadataTest#testCompatibilityR [4].
44     *
45     * R (audio HAL 6.0) defined keys are as follows [2]:
46     * "bitrate", int32
47     * "channel-mask", int32
48     * "mime", string
49     * "sample-rate", int32
50     * "bit-width", int32
51     * "has-atmos", int32
52     * "audio-encoding", int32
53     *
54     * S (audio HAL 7.0) in addition adds the following keys:
55     * "presentation-id", int32
56     * "program-id", int32
57     * "presentation-content-classifier", int32
58     *    presentation-content-classifier key values can be referenced from
59     *    frameworks/base/media/java/android/media/AudioPresentation.java
60     *    i.e AudioPresentation.ContentClassifier
61     *    It can contain any of the below values
62     *    CONTENT_UNKNOWN   = -1,
63     *    CONTENT_MAIN      =  0,
64     *    CONTENT_MUSIC_AND_EFFECTS = 1,
65     *    CONTENT_VISUALLY_IMPAIRED = 2,
66     *    CONTENT_HEARING_IMPAIRED  = 3,
67     *    CONTENT_DIALOG = 4,
68     *    CONTENT_COMMENTARY = 5,
69     *    CONTENT_EMERGENCY = 6,
70     *    CONTENT_VOICEOVER = 7
71     * "presentation-language", string  // represents ISO 639-2 (three letter code)
72     *
73     * Parceling Format:
74     * All values are native endian order. [1]
75     *
76     * using type_size_t = uint32_t;
77     * using index_size_t = uint32_t;
78     * using datum_size_t = uint32_t;
79     *
80     * Permitted type indexes are
81     * TYPE_NONE = 0, // Reserved
82     * TYPE_INT32 = 1,
83     * TYPE_INT64 = 2,
84     * TYPE_FLOAT = 3,
85     * TYPE_DOUBLE = 4,
86     * TYPE_STRING = 5,
87     * TYPE_DATA = 6,  // A data table of <String, Datum>
88     *
89     * Datum = {
90     *           (type_size_t)  Type (the type index from type_as_value<T>.)
91     *           (datum_size_t) Size (size of the Payload)
92     *           (byte string)  Payload<Type>
93     *         }
94     *
95     * The data is specified in native endian order.
96     * Since the size of the Payload is always present, unknown types may be skipped.
97     *
98     * Payload<Fixed-size Primitive_Value>
99     * [ sizeof(Primitive_Value) in raw bytes ]
100     *
101     * Example of Payload<Int32> of 123:
102     * Payload<Int32>
103     * [ value of 123                   ] =  0x7b 0x00 0x00 0x00       123
104     *
105     * Payload<String>
106     * [ (index_size_t) length, not including zero terminator.]
107     * [ (length) raw bytes ]
108     *
109     * Example of Payload<String> of std::string("hi"):
110     * [ (index_size_t) length          ] = 0x02 0x00 0x00 0x00        2 strlen("hi")
111     * [ raw bytes "hi"                 ] = 0x68 0x69                  "hi"
112     *
113     * Payload<Data>
114     * [ (index_size_t) entries ]
115     * [ raw bytes   (entry 1) Key   (Payload<String>)
116     *                         Value (Datum)
117     *                ...  (until #entries) ]
118     *
119     * Example of Payload<Data> of {{"hello", "world"},
120     *                              {"value", (int32_t)1000}};
121     * [ (index_size_t) #entries        ] = 0x02 0x00 0x00 0x00        2 entries
122     *    Key (Payload<String>)
123     *    [ index_size_t length         ] = 0x05 0x00 0x00 0x00        5 strlen("hello")
124     *    [ raw bytes "hello"           ] = 0x68 0x65 0x6c 0x6c 0x6f   "hello"
125     *    Value (Datum)
126     *    [ (type_size_t) type          ] = 0x05 0x00 0x00 0x00        5 (TYPE_STRING)
127     *    [ (datum_size_t) size         ] = 0x09 0x00 0x00 0x00        sizeof(index_size_t) +
128     *                                                                 strlen("world")
129     *       Payload<String>
130     *       [ (index_size_t) length    ] = 0x05 0x00 0x00 0x00        5 strlen("world")
131     *       [ raw bytes "world"        ] = 0x77 0x6f 0x72 0x6c 0x64   "world"
132     *    Key (Payload<String>)
133     *    [ index_size_t length         ] = 0x05 0x00 0x00 0x00        5 strlen("value")
134     *    [ raw bytes "value"           ] = 0x76 0x61 0x6c 0x75 0x65   "value"
135     *    Value (Datum)
136     *    [ (type_size_t) type          ] = 0x01 0x00 0x00 0x00        1 (TYPE_INT32)
137     *    [ (datum_size_t) size         ] = 0x04 0x00 0x00 0x00        4 sizeof(int32_t)
138     *        Payload<Int32>
139     *        [ raw bytes 1000          ] = 0xe8 0x03 0x00 0x00        1000
140     *
141     * The contents of audioMetadata is a Payload<Data>.
142     * An implementation dependent detail is that the Keys are always
143     * stored sorted, so the byte string representation generated is unique.
144     *
145     * Vendor keys are allowed for informational and debugging purposes.
146     * Vendor keys should consist of the vendor company name followed
147     * by a dot; for example, "vendorCompany.someVolume" [2].
148     *
149     * [1] system/media/audio_utils/include/audio_utils/Metadata.h
150     * [2] frameworks/base/media/java/android/media/AudioMetadata.java
151     * [3] system/media/audio_utils/tests/metadata_tests.cpp
152     * [4] cts/tests/tests/media/src/android/media/cts/AudioMetadataTest.java
153     *
154     * @param audioMetadata is a buffer containing decoded format changes
155     *     reported by codec. The buffer contains data that can be transformed
156     *     to audio metadata, which is a C++ object based map.
157     */
158    oneway onCodecFormatChanged(vec<uint8_t> audioMetadata);
159};
160