1# DRM Media Key Session Management (C/C++)
2
3The **MediaKeySystem** class of the DRM module supports media key management and media decryption. **MediaKeySession** instances are created and destroyed by **MediaKeySystem** instances.
4
5## How to Develop
6
7Read [DRM](../../reference/apis-drm-kit/_drm.md) for the API reference.
8
91. Import the NDK, which provides DRM-related attributes and methods.
10
11   ```c++
12    #include "multimedia/drm_framework/native_drm_common.h"
13    #include "multimedia/drm_framework/native_drm_err.h"
14    #include "multimedia/drm_framework/native_mediakeysession.h"
15    #include "multimedia/drm_framework/native_mediakeysystem.h"
16   ```
17
182. Link the DRM NDK dynamic library in the CMake script.
19
20   ```txt
21    target_link_libraries(PUBLIC libnative_drm.so)
22   ```
23
243. Declare the MediaKeySystem event listener callback.
25
26    ```c++
27    // This callback applies to the scenario where there is only one MediaKeySystem instance.
28    static Drm_ErrCode SessoinEventCallBack(DRM_EventType  eventType, uint8_t *info, int32_t infoLen, char *extra)
29    {
30        return DRM_ERR_OK;
31    }
32
33    static Drm_ErrCode SessoinKeyChangeCallBack(DRM_KeysInfo *keysInfo, bool newKeysAvailable)
34    {
35        return DRM_ERR_OK;
36    }
37
38    // This callback applies to the scenario where there are multiple MediaKeySystem instances.
39    static Drm_ErrCode SessoinEventCallBackWithObj(MediaKeySession *mediaKeySessoin, DRM_EventType eventType, uint8_t *info, int32_t infoLen, char *extra)
40    {
41        return DRM_ERR_OK;
42    }
43
44    static Drm_ErrCode SessoinKeyChangeCallBackWithObj(MediaKeySession *mediaKeySessoin, DRM_KeysInfo *keysInfo, bool hasNewGoodKeys)
45    {
46        return DRM_ERR_OK;
47    }
48    ```
49
504. Set the MediaKeySystem event listener callback.
51
52    ```c++
53    // This callback applies to the scenario where there is only one MediaKeySystem instance.
54    MediaKeySession_Callback sessionCallback = { SessoinEventCallBack, SessoinKeyChangeCallBack };
55    Drm_ErrCode ret = OH_MediaKeySession_SetMediaKeySessionCallback(mediaKeySession, &sessionCallback);
56    if (ret != DRM_ERR_OK) {
57        printf("OH_MediaKeySession_SetMediaKeySessionCallback failed.");
58    }
59
60    // This callback applies to the scenario where there are multiple MediaKeySystem instances.
61    OH_MediaKeySession_Callback sessionCallback = { SessoinEventCallBackWithObj, SessoinKeyChangeCallBackWithObj };
62    ret = OH_MediaKeySession_SetCallback(mediaKeySession, &sessionCallback);
63    if (ret != DRM_ERR_OK) {
64        printf("OH_MediaKeySession_SetCallback failed.");
65    }
66    ```
67
685. Generate a media key request and process its response.
69
70    ```c++
71    DRM_MediaKeyRequest mediaKeyRequest;
72    DRM_MediaKeyRequestInfo info;
73    // initData corresponds to the PSSH data in the stream. Pass in the actual data.
74    unsigned char initData[128] = {0x00};
75    memset_s(&info, sizeof(DRM_MediaKeyRequestInfo), 0, sizeof(DRM_MediaKeyRequestInfo));
76    info.initDataLen = sizeof(initData);
77    info.type = MEDIA_KEY_TYPE_ONLINE;
78    memcpy_s(info.mimeType, sizeof("video/avc"), (char *)"video/avc", sizeof("video/avc"));
79    memcpy_s(info.initData, sizeof(initData), initData, sizeof(initData));
80    memcpy_s(info.optionName[0], sizeof("optionalDataName"), (char *)"optionalDataName", sizeof("optionalDataName"));
81    memcpy_s(info.optionData[0], sizeof("optionalDataValue"), (char *)"optionalDataValue", sizeof("optionalDataValue"));
82    info.optionsCount = 1;
83    ret = OH_MediaKeySession_GenerateMediaKeyRequest(mediaKeySession, &info, &mediaKeyRequest);
84    if (ret != DRM_ERR_OK) {
85        printf("OH_MediaKeySession_GenerateMediaKeyRequest failed.");
86    }
87    /* The composition of an offline media key ID varies according to the DRM scheme. You can obtain an ID in either of the following ways:
88      1. The application calls OH_MediaKeySystem_GetOfflineMediaKeyIds to obtain the ID.
89      2. The application requests the DRM service through the network, obtains a keySessionResponse, and sends the response to OH_MediaKeySession_ProcessMediaKeyResponse for parsing.
90         An offline media key ID is obtained. The maximum length of a media key ID is 128. The following code is an example. Set the media key ID based on the actual media key data and length.
91    */
92    unsigned char mediaKeyId[26] = {0x00};
93    int32_t mediaKeyIdLen = 26;
94    // The maximum length of a media key response is 12288. Enter the actual length.
95    unsigned char mediaKeyResponse[12288] = {0x00};
96    int32_t mediaKeyResponseLen = 12288;
97    ret = OH_MediaKeySession_ProcessMediaKeyResponse(mediaKeySession, mediaKeyResponse,
98        mediaKeyResponseLen, mediaKeyId, &mediaKeyIdLen);
99    if (ret != DRM_ERR_OK) {
100        printf("OH_MediaKeySession_ProcessMediaKeyResponse failed.");
101    }
102    ```
103
1046. (Optional) Check the media key status of the media key session.
105
106    ```c++
107    DRM_MediaKeyStatus mediaKeyStatus;
108    ret = OH_MediaKeySession_CheckMediaKeyStatus(mediaKeySession, &mediaKeyStatus);
109    if (ret != DRM_ERR_OK) {
110        printf("OH_MediaKeySession_CheckMediaKeyStatus failed.");
111    }
112    ```
113
1147. (Optional) Clear all media keys in the media key session.
115
116    ```c++
117    ret = OH_MediaKeySession_ClearMediaKeys(mediaKeySession);
118    if (ret != DRM_ERR_OK) {
119        printf("OH_MediaKeySession_ClearMediaKeys failed.");
120    }
121   ```
122
1238. (Optional) Generate an offline media key release request and process its response.
124
125    ```c++
126    uint8_t releaseRequest[MAX_MEDIA_KEY_REQUEST_DATA_LEN];
127    int32_t releaseRequestLen = MAX_MEDIA_KEY_REQUEST_DATA_LEN;
128    ret = OH_MediaKeySession_GenerateOfflineReleaseRequest(mediaKeySession,
129        mediaKeyId, mediaKeyIdLen, releaseRequest, &releaseRequestLen);
130    if (ret != DRM_ERR_OK) {
131        printf("OH_MediaKeySession_GenerateOfflineReleaseRequest failed.");
132    }
133    // keyReleaseResponse is obtained from the DRM service through the network request using the request body releaseRequest. Pass in the actual data obtained.
134    unsigned char keyReleaseResponse[12288] = {0x00};
135    int32_t keyReleaseResponseLen = 12288;
136    ret = OH_MediaKeySession_ProcessOfflineReleaseResponse(mediaKeySession, mediaKeyId, mediaKeyIdLen,
137       keyReleaseResponse, keyReleaseResponseLen);
138    if (ret != DRM_ERR_OK) {
139        printf("OH_MediaKeySession_ProcessOfflineReleaseResponse failed.");
140    }
141    ```
142
1439. (Optional) Restore offline media keys.
144
145    ```c++
146    // Load the media key with the specified media key ID to the current session. The loaded media key can belong to the current session or another session.
147    ret = OH_MediaKeySession_RestoreOfflineMediaKeys(mediaKeySession, mediaKeyId, mediaKeyIdLen);
148    if (ret != DRM_ERR_OK) {
149        printf("OH_MediaKeySession_RestoreOfflineMediaKeys failed.");
150    }
151   ```
152
15310. (Optional) Call **OH_MediaKeySession_GetContentProtectionLevel** in the **MediaKeySession** class to obtain the content protection level of the current session.
154
155    ```c++
156    DRM_ContentProtectionLevel sessionContentProtectionLevel;
157    ret = OH_MediaKeySession_GetContentProtectionLevel(mediaKeySession,
158        &sessionContentProtectionLevel);
159    if (ret != DRM_ERR_OK) {
160        printf("OH_MediaKeySession_GetContentProtectionLevel failed.");
161    }
162    ```
163
16411. (Optional) Check whether secure decoding is required.
165
166    ```c++
167    bool requireSecureDecoder;
168    ret = OH_MediaKeySession_RequireSecureDecoderModule(mediaKeySession, "video/avc", &requireSecureDecoder);
169    if (ret != DRM_ERR_OK) {
170        printf("OH_MediaKeySession_RequireSecureDecoderModule failed.");
171    }
172    ```
173