1# OH_AVDataSourceExt 2 3## Overview 4 5The struct describes a user-defined data source. User-defined data can be passed to its callback functions through the **userData** parameter. 6 7**Since**: 20 8 9**Related module**: [CodecBase](capi-codecbase.md) 10 11**Header file**: [native_avcodec_base.h](capi-native-avcodec-base-h.md) 12 13## Summary 14 15### Member Variables 16 17| Name| Description| 18| -- | -- | 19| int64_t size | Size of the data source.| 20| [OH_AVDataSourceReadAtExt](capi-native-avcodec-base-h.md#oh_avdatasourcereadatext) readAt | Callback of the data source.| 21