1e41f4b71Sopenharmony_ci# Audio/Video Overview 2e41f4b71Sopenharmony_ci 3e41f4b71Sopenharmony_ci 4e41f4b71Sopenharmony_ciOpenHarmony multimedia services help you to develop audio and video playback and recording. 5e41f4b71Sopenharmony_ci 6e41f4b71Sopenharmony_ci 7e41f4b71Sopenharmony_ci- The media playback module facilitates the development of audio and video playback, including media file and stream playback, volume control, and playback progress control. 8e41f4b71Sopenharmony_ci 9e41f4b71Sopenharmony_ci- The media recording module supports the development of audio and video recording and provides functions to set the size of captured video, encoding bit rate, encoder type, video frame rate, audio sampling rate, and output file format. 10e41f4b71Sopenharmony_ci 11e41f4b71Sopenharmony_ci 12e41f4b71Sopenharmony_ci## Basic Concepts 13e41f4b71Sopenharmony_ci 14e41f4b71Sopenharmony_ciIt is considered good practice that you understand the following concepts before starting development: 15e41f4b71Sopenharmony_ci 16e41f4b71Sopenharmony_ci- Streaming media technology 17e41f4b71Sopenharmony_ci 18e41f4b71Sopenharmony_ci The streaming media technology refers to a process to encode continuous video and audio data and store the data on a network server. A viewer can watch and listen to the video and audio during download with no need to wait for the completion of download. 19e41f4b71Sopenharmony_ci 20e41f4b71Sopenharmony_ci- Video frame rate 21e41f4b71Sopenharmony_ci 22e41f4b71Sopenharmony_ci The frame rate is used to measure the number of displayed frames, which is the number of images transmitted per second. The more frames per second (FPS), the smoother the video. 23e41f4b71Sopenharmony_ci 24e41f4b71Sopenharmony_ci- Bit rate 25e41f4b71Sopenharmony_ci 26e41f4b71Sopenharmony_ci Bit rate is the number of bits transmitted per unit of time. The commonly used unit is kbit/s. 27e41f4b71Sopenharmony_ci 28e41f4b71Sopenharmony_ci- Sampling rate 29e41f4b71Sopenharmony_ci 30e41f4b71Sopenharmony_ci The sampling rate is the number of samples per second taken from continuous signals to form discrete signals. The unit is hertz (Hz). 31e41f4b71Sopenharmony_ci 32e41f4b71Sopenharmony_ci 33e41f4b71Sopenharmony_ci## Codec Specifications 34e41f4b71Sopenharmony_ci 35e41f4b71Sopenharmony_ciAvailable audio and video codecs vary depending on device types. The following table lists supported specifications for available development boards. 36e41f4b71Sopenharmony_ci 37e41f4b71Sopenharmony_ci**Table 1** Codec specifications for different development boards 38e41f4b71Sopenharmony_ci 39e41f4b71Sopenharmony_ci| Device Type| Development Board| Decoding| Encoding| 40e41f4b71Sopenharmony_ci| -------- | -------- | -------- | -------- | 41e41f4b71Sopenharmony_ci| Cameras with a screen| Hi3516 | - Audio: MPEG-4 AAC Profile (AAC LC), mono and dual channels, MPEG-4 (.mp4 and .m4a) <br>- Video: The H.265 (HEVC) and H.264 (AVC) (for streams encoded using a chip of the same type) and the MPEG-4 (.mp4) container format are supported.| - Audio: AAC-LC encoding, mono and dual channels, and the MPEG-4 (.mp4) container format are supported.<br>- Video: H.264 and H.265 encoding and the MPEG-4 (.mp4) container format are supported.| 42e41f4b71Sopenharmony_ci| Cameras without a screen| Hi3518 | - Audio: MPEG-4 AAC Profile (AAC LC), mono and dual channels, and the MPEG-4 (.mp4 and .m4a) container format are supported.<br>- Video: none| - Audio: AAC-LC encoding, mono and dual channels, and the MPEG-4 (.mp4) container format are supported.<br>- Video: H.264 and H.265 encoding and the MPEG-4 (.mp4) container format are supported.| 43e41f4b71Sopenharmony_ci| WLAN connecting devices| Hi3861 | N/A| N/A| 44e41f4b71Sopenharmony_ci 45e41f4b71Sopenharmony_ciFor details about the codec specifications of Hi3516 and Hi3518, refer to their documentation. 46