请问各位大虾，我想用DM365的CMEM做预录像功能，发现去读它的GetAVData().，只能读到比当前帧提前240帧，我一秒是30帧，只能提前8秒，请问我怎么设置才能读多此之前的帧。是不是只改下面的MP4_MEM_SIZE，我改过了，但最多就240帧。还有哪些地方可以改的吗？
#define MJPG_CACHE_SIZE (0x200000)
/* size of 3 GOP */
#define MP4_CACHE_SIZE (0x600000) //(0x600000)m
#define MP4_EXT_CACHE_SIZE (0x300000) //0x300000
#define AUDIO_CACHE_SIZE (0x80000)
#define MJPG_CACHE_BLK_SIZE (100*1024)
#define MP4_CACHE_BLK_SIZE (30*1024)
#define MP4_EXT_CACHE_BLK_SIZE (10*1024)
#define AUDIO_CACHE_BLK_SIZE (1*1024)
#define CACHE_MEM_SIZE (MJPG_CACHE_SIZE+MP4_CACHE_SIZE+MP4_EXT_CACHE_SIZE+AUDIO_CACHE_SIZE)
#define MJPG_MEM_SIZE (0x200000)
#define MP4_MEM_SIZE (0xa00000) //(0x600000)
#define MP4_EXT_MEM_SIZE (0x300000) //0x300000
#define AUDIO_MEM_SIZE (0x80000)
#define MJPG_BLK_SIZE (100*1024)
#define MP4_BLK_SIZE (30*1024)
#define MP4_EXT_BLK_SIZE (10*1024)
#define AUDIO_BLK_SIZE (1*1024)
