  We address the problem of decoding video file fragments when the necessary
encoding parameters are missing. With this objective, we propose a method that
automatically generates H.264 video headers containing these parameters and
extracts coded pictures in the partially available compressed video data. To
accomplish this, we examined a very large corpus of videos to learn patterns of
encoding settings commonly used by encoders and created a parameter dictionary.
Further, to facilitate a more efficient search our method identifies
characteristics of a coded bitstream to discriminate the entropy coding mode.
It also utilizes the application logs created by the decoder to identify
correct parameter values. Evaluation of the effectiveness of the proposed
method on more than 55K videos with diverse provenance shows that it can
generate valid headers on average in 11.3 decoding trials per video. This
result represents an improvement by more than a factor of 10 over the
conventional approach of video header stitching to recover video file
fragments.
