[How] Flash: Seek() & PlayHeadTime() Accuracy

Using seek() and PlayHeadTime() with FLVPlayback component of video files in Flash can be quite inaccurate. We had the same problem when we were building a prototype for our project, which involved switching and syncing of videos using specific timing. PlayHeadTime gave a decimal value, but whenever we would do a seek() using the PlayHeadTime value on a video, the timing would be off by 0.5-1 second.

Apparently, the accuracy of the seek() function is dependent on the keyFrameInterval of the video and the FPS meaning Precision = keyFrameInterval / FPS.

So for example, if you have a keyFrameInterval = 30 (1st frame will be a keyframe, 30th frame will be a keyframe, 60th frame … etc.) and FPS is set on 15, you’ll only be able to seek in 2-seconds intervals of time (precision = 30 / 15).

To make the seeking more accurate, set the key frame distance when exporting your video with Adobe Premiere. This option can be found in the “video” tab, “Advanced Settings”, check “Set Key Frame Distance” and set the key frame distance lower. Export it and now your seek() accuracy would be more precise!