A delay estimation method for a smart rearview mirror, comprising: obtaining (101; 401) identification information of an external device in response to connecting with the external device by a smart rearview mirror for screen projection; determining a target delay estimation upper limit corresponding to the external device based on the identification information; obtaining (103; 410) a delay estimation result by performing a delay estimation based on the target delay estimation upper limit in response to sending a voice signal by the smart rearview mirror to the external device; and performing (104; 411) a delay processing on the voice signal based on the delay estimation result; wherein determining the target delay estimation upper limit corresponding to the external device based on the identification information comprises: searching (201; 302; 403) in an upper limit configuration file based on the identification information, wherein the upper limit configuration file comprises a correspondence between the identification information and delay estimation upper limits; determining (202; 303; 404) whether there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file; in response to that there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (203; 304; 405) the delay estimation upper limit corresponding to the identification information of the external device as the target delay estimation upper limit; and in response to that there is no delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (204; 305; 406) a preset delay estimation upper limit as the target delay estimation upper limit corresponding to the external device. obtaining (101; 401) identification information of an external device in response to connecting with the external device by a smart rearview mirror for screen projection; determining a target delay estimation upper limit corresponding to the external device based on the identification information; obtaining (103; 410) a delay estimation result by performing a delay estimation based on the target delay estimation upper limit in response to sending a voice signal by the smart rearview mirror to the external device; and performing (104; 411) a delay processing on the voice signal based on the delay estimation result; wherein determining the target delay estimation upper limit corresponding to the external device based on the identification information comprises: searching (201; 302; 403) in an upper limit configuration file based on the identification information, wherein the upper limit configuration file comprises a correspondence between the identification information and delay estimation upper limits; determining (202; 303; 404) whether there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file; in response to that there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (203; 304; 405) the delay estimation upper limit corresponding to the identification information of the external device as the target delay estimation upper limit; and in response to that there is no delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (204; 305; 406) a preset delay estimation upper limit as the target delay estimation upper limit corresponding to the external device. searching (201; 302; 403) in an upper limit configuration file based on the identification information, wherein the upper limit configuration file comprises a correspondence between the identification information and delay estimation upper limits; determining (202; 303; 404) whether there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file; in response to that there is a delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (203; 304; 405) the delay estimation upper limit corresponding to the identification information of the external device as the target delay estimation upper limit; and in response to that there is no delay estimation upper limit corresponding to the identification information of the external device in the upper limit configuration file, determining (204; 305; 406) a preset delay estimation upper limit as the target delay estimation upper limit corresponding to the external device.