> ## Documentation Index > Fetch the complete documentation index at: https://docs.stmlink.com/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > 对外开放的服务端接口有两组前缀，都用同一套鉴权：`/server/v1/...`（SRTC 与 SMeeting 的主接口）和 `/stm/srvapi/v1/...`（SMeeting 的用户体系，服务端极简对接会用到）。鉴权是 app_id + nonce + timestamp + signature 四个请求头，用 app_key 做 HMAC-SHA256 签名，只能从业务方自己的后端调用。除这两组前缀外的接口均为内部接口，不要建议客户调用。 Public server APIs use two path prefixes with the same authentication: `/server/v1/...` (the main APIs of both SRTC and SMeeting) and `/stm/srvapi/v1/...` (the SMeeting user system, used by server-side low-code integration). Authenticate with four request headers, app_id + nonce + timestamp + signature, where signature is HMAC-SHA256 keyed with app_key; call these APIs only from the customer's own backend. Any other path is internal: never suggest calling it. > app_key 是服务端密钥，绝不能出现在客户端代码、前端配置或移动 App 里。客户端加入频道用的 token 必须由业务方后端签发后下发（SRTC 走 `/server/v1/channel/grant`，SMeeting 走 `/stm/srvapi/v1/member/grant`）。 app_key is a server-side secret and must never appear in client code, frontend config, or a mobile app. The token a client uses to join must be issued by the customer's backend and passed down to the client (SRTC: `/server/v1/channel/grant`; SMeeting: `/stm/srvapi/v1/member/grant`). > SRTC 与 SMeeting 是上下两层不同的产品，术语不通用：SRTC 是音视频底座，说「频道 channel」「加入 / 退出」；SMeeting 建在 SRTC 之上，说「房间 room」「会议 meeting」「进入 / 退出」。回答时按用户所在的层用对应术语，不要把「房间」「会议」安到 SRTC 的接口上，也不要用「频道」「加入 / 离开」描述 SMeeting 的概念（接口标识符原样保留）。 SRTC and SMeeting are two separate layers with different terminology. SRTC is the audio/video foundation: it has channels, and users join and leave a channel. SMeeting is built on top of SRTC: it has rooms and meetings, and members enter and exit a meeting. Answer in the terms of the layer the user is working with: never apply "room" or "meeting" to SRTC APIs, and never describe SMeeting concepts in prose with "channel", "join", or "leave" (API identifiers such as `force_join` keep their literal names). > 同一能力在各端 SDK 里的包名、类名、方法名并不相同。写示例代码时请使用文档中该端自己的 API，不要把一个端的写法套到另一个端上。苹果平台每个产品都有两套 SDK（Swift 原生与 Objective-C），两套 API 不能混用。 Package, class, and method names differ between platform SDKs for the same capability. In sample code, use the API documented for that platform; never carry one platform's code over to another. On Apple platforms each product ships two SDKs (native Swift and Objective-C) whose APIs must not be mixed. # Media quality > Field-level data dictionary for Android SRTC media quality statistics in MediaMetric: the overall Metric, server-side uplink/downlink QualityReport, network, upload, and download stats, and per-track audio/video sender and receiver stats. Read when interpreting onMediaMetric data. ## Description This page is compiled from the data classes (`data class`) in `MediaMetric.kt` and serves as a field-level data dictionary.\ It doesn't cover interface (`interface`) definitions. For how to get quality data (subscription callbacks / active queries) and how to handle poor networks, see [Network quality](/en/rtc/android/network-quality). ## MediaMetric.Metric The overall media quality statistics object. | Property | Data type | Description | | - | - | - | | localAudios | `MutableMap` | Local audio stats (by user track). | | localVideos | `MutableMap` | Local video stats (by user track). | | remoteAudios | `MutableMap` | Remote audio stats (by user track). | | remoteVideos | `MutableMap` | Remote video stats (by user track). | | localUploadStats | LocalUploadStats | Local upload overview stats. | | remoteDownloadStats | `MutableMap` | Remote download stats (by `uid`). | | networkStats | NetworkStats | Network status stats. | | qualityReport | QualityReport? | Uplink/downlink quality report additionally sent by the server; `null` until the first report arrives. | ## MediaMetric.QualityReport The uplink/downlink connection quality report computed and sent by the server, distinguishing uplink (this client to the server) from downlink (the server to this client). | Property | Data type | Description | | - | - | - | | timestamp | Long | Timestamp (ms) when the server generated the quality report. | | uplink | QualityStats | Uplink quality from this client to the server. | | downlink | QualityStats | Downlink quality from the server to this client. | ## MediaMetric.QualityStats A quality sample for one direction of the link (uplink or downlink). | Property | Data type | Description | | - | - | - | | score | Double | Overall quality score, 0–100; higher is better. | | level | String | Quality level: `excellent` / `good` / `poor` / `lost`. | | mos | Double | Estimated voice MOS (mean opinion score), 1.0–4.5; higher is better. | | loss | Double | Packet loss rate, 0–1. | | rtt | Double | Round-trip time (ms). | | jitter | Double | Jitter (ms). | | packets | Long | Number of packets included in this round of statistics. | | bitrate | Double | Average bitrate (kbps). | | bytes | Long | Bytes in this window. | ## MediaMetric.LocalMetric The local aggregated statistics object (Map keys are `String`). | Property | Data type | Description | | - | - | - | | localAudios | `MutableMap` | Local audio stats. | | localVideos | `MutableMap` | Local video stats. | | remoteAudios | `MutableMap` | Remote audio stats. | | remoteVideos | `MutableMap` | Remote video stats. | | networkStats | NetworkStats | Network status stats. | ## MediaMetric.NetworkStats The network status statistics object. | Property | Data type | Description | | - | - | - | | bitrateUp | Float | Uplink bitrate (kb/s). | | bitrateDown | Float | Downlink bitrate (kb/s). | | delay | Float | Delay. | | lossrateUp | Float | Uplink packet loss rate. | | lossrateDown | Float | Downlink packet loss rate. | | pktUp | Long | Uplink packet count. | | pktDown | Long | Downlink packet count. | | pktLossUp | Long | Uplink packets lost. | | pktLossDown | Long | Downlink packets lost. | ## MediaMetric.LocalUploadStats The local upload statistics object. | Property | Data type | Description | | - | - | - | | uid | String | User ID. | | delay | Float | Upload delay. | | videoBitrate | Float | Video upload bitrate (kb/s). | | audioBitrate | Float | Audio upload bitrate (kb/s). | | lossrate | Float | Packet loss rate. | ## MediaMetric.RemoteDownloadStats The remote download statistics object. | Property | Data type | Description | | - | - | - | | uid | String | User ID. | | audioPacketsReceived | Long | Audio packets received. | | videoPacketsReceived | Long | Video packets received (including retransmitted packets). | | packetsLost | Long | Packets lost. | | retransmittedPackets | Long | Retransmitted packets (video). | | lossrate | Float | Packet loss rate. | | audioBitrate | Float | Audio bitrate (kb/s). | | videoBitrate | Float | Video bitrate (kb/s). | ## MediaMetric.AudioSenderStats The audio sender statistics object. | Property | Data type | Description | | - | - | - | | audioLevel | Float | Audio energy. | | trackId | String | Track ID. | | packetsSent | Long | Packets sent. | | byteSent | Long | Bytes sent. | | bitrateSent | Float | Send bitrate (kb/s). | | jitter | Float | Network jitter. | | packetsLost | Int | Packets lost (retransmissions not deducted). | | roundTripTime | Float | Round-trip time. | | mimeType | String | Codec type. | | timestamp | Long | Timestamp (ms). | | type | String | Media type, always `audio`. | ## MediaMetric.VideoSenderStats The video sender statistics object. | Property | Data type | Description | | - | - | - | | firCount | Long | Number of requests to send an I-frame. | | pliCount | Long | Number of PLI (Picture Loss Indication) requests, i.e., keyframe requests. | | nackCount | Long | Number of requests to retransmit lost RTP packets. | | rid | String | Simulcast stream identifier. | | frameWidth | Int | Video frame width. | | frameHeight | Int | Video frame height. | | framesPerSecond | Float | Video frame rate (fps). | | frameSent | Long | Frames sent. | | qualityLimitationReason | String | The main reason quality is limited (such as none/cpu/bandwidth/other/inactive). | | qualityLimitationDurations | `Map` | Cumulative duration of each limitation reason (seconds). | | qualityLImitationResolutionChange | Long | Number of resolution changes caused by quality limitation. | | retransmittedPacketsSent | Long | RTP packets retransmitted. | | targetBitrate | Float | Encoder target bitrate (bps). | | trackId | String | Track ID. | | packetsSent | Long | Packets sent. | | byteSent | Long | Bytes sent. | | bitrateSent | Float | Send bitrate (kb/s). | | jitter | Float | Network jitter. | | packetsLost | Int | Packets lost (retransmissions not deducted). | | roundTripTime | Float | Round-trip time. | | mimeType | String | Codec type. | | timestamp | Long | Timestamp (ms). | | type | String | Media type, always `video`. | ## MediaMetric.AudioReceiverStats The audio receiver statistics object. | Property | Data type | Description | | - | - | - | | audioLevel | Float | Audio energy. | | concealedSamples | Long | Total audio samples recovered by concealment. | | concealEvents | Long | Number of interpolation operations. | | silentConcealedSamples | Long | Number of samples concealed as silence. | | silentConcealmentEvents | Long | Number of silent concealment events. | | totalAudioEnergy | Double | Cumulative received audio energy. | | totalSamplesDuration | Double | Cumulative playback duration (seconds). | | trackId | String | Track ID. | | packetsReceived | Long | Packets received. | | bytesReceived | Long | Bytes received. | | bitrateReceived | Float | Receive bitrate (kb/s). | | jitter | Float | Network jitter. | | jitterBufferDelay | Float | Cumulative jitter buffer delay. | | packetsLost | Int | Packets lost (retransmissions not deducted). | | mimeType | String | Codec type. | | timestamp | Long | Timestamp (ms). | | type | String | Media type, always `audio`. | ## MediaMetric.VideoReceiverStats The video receiver statistics object. | Property | Data type | Description | | - | - | - | | framesDecoded | Long | Frames decoded successfully. | | framesDropped | Long | Frames dropped during decoding. | | framesReceived | Long | Total frames received. | | framesPerSecond | Float | Receive frame rate (fps). | | frameWidth | Int | Received frame width. | | frameHeight | Int | Received frame height. | | firCount | Int | Number of requests to send an I-frame. | | pliCount | Int | Number of PLI (Picture Loss Indication) requests, i.e., keyframe requests. | | nackCount | Int | Number of requests to retransmit lost RTP packets. | | retransmittedPacketsReceived | Long | Retransmitted packets counted by the receiver. | | decoderImplementation | String | Decoder implementation name. | | trackId | String | Track ID. | | packetsReceived | Long | Packets received. | | bytesReceived | Long | Bytes received. | | bitrateReceived | Float | Receive bitrate (kb/s). | | jitter | Float | Network jitter. | | jitterBufferDelay | Float | Cumulative jitter buffer delay. | | packetsLost | Int | Packets lost (retransmissions not deducted). | | mimeType | String | Codec type. | | timestamp | Long | Timestamp (ms). | | type | String | Media type, always `video`. |