More than 1 million consumers canceled their cable-TV or satellite subscriptions in the past quarter, one of the largest seasonal drops ever, stepping up pressure on pay-TV providers to generate revenue in other ways.

Old-guard companies have turned to streaming services and partnerships with digital video startups to stanch the loss of pay-TV subscribers and convert some into different kinds of customers. Yet figures reviewed by The Wall Street Journal show that those tactics have failed to offset the erosion of what used...