Methods for generating an AV bitstream (e.g., an MPEG-2 transport stream or bitstream segment having adaptive streaming format) such that the AV bitstream includes at least one video I-frame synchronized with at least one audio I-frame, e.g., including by re-authoring at least one video or audio frame (as a re-authored I-frame or a re-authored P-frame). Typically, a segment of content of the AV bitstream which includes the re-authored frame starts with an I-frame and includes at least one subsequent P-frame. Other aspects are methods for adapting such an AV bitstream, audio/video processing units configured to perform any embodiment of the inventive method, and audio/video processing units which include a buffer memory which stores at least one segment of an AV bitstream generated in accordance with any embodiment of the inventive method.