The invention relates to a
digital multimedia evidence obtaining method and device. The
digital multimedia evidence obtaining method comprises the steps that a multi-
modal knowledge graph is constructed based on multi-
modal media samples, and the multi-
modal media samples comprise image frames, audio signals and text subtitles; identifying potential forgery risk points from the multi-modal media sample, and generating a forgery task graph for the potential forgery risk points; performing multi-modal
feature extraction on the multi-modal media sample based on the forgery task graph to obtain a multi-
granularity forgery clue set; structuring the multi-
granularity forged clue set into knowledge entries; chain logic reasoning is carried out based on the multi-modal
knowledge graph and the knowledge entries, and cross-modal consistency scores are calculated to generate a reasoning tree; determining a final forgery credibility
score based on the confidence of each node in the
inference tree; and based on the final forgery credibility
score, determining whether forgery content exists in the multi-modal media sample. With the adoption of the method and the device, high-precision and high-robustness forged content identification can be realized.