[Mp4-tech] Unrestricted Motion Vectors

[Gary Sullivan]

Yes, it can use them.  If the encoder does not want to use them, it can indicate that it is not using them by setting the syntax element called motion_vectors_over_pic_boundaries_flag equal to 0.
Exact text is as follows.  It should be sufficiently clear for you to understand the exact meaning in regard to your question about interpolation details with respect to the definition of the feature:
"motion_vectors_over_pic_boundaries_flag equal to 0 indicates that no sample outside the picture boundaries and no sample at a fractional sample position whose value is derived using one or more samples outside the picture boundaries is used to inter predict any sample. motion_vectors_over_pic_boundaries_flag equal to 1 indicates that one or more samples outside picture boundaries may be used in inter prediction. When the motion_vectors_over_pic_boundaries_flag syntax element is not present, motion_vectors_over_pic_boundaries_flag value shall be inferred to be equal to 1."
Best Regards
Gary Sullivan
________________________________
From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Chaitanya Atluru
Sent: Wednesday, May 28, 2024 4:56 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] Unrestricted Motion Vectors
Hi,
    Can someone explain if H.264 (mpeg 4  part 10) uses Unrestricted Motion Vector (UMV). In H.263 there is an option to restrict MV's to stay inside a frame. If H.264 restricts MV's does it mean that the extra pixels (eg: if a 4x4 partition is taken it actually requires 9x9 partition for interpolation of half and quarter pels) needed for interpolation can fall outside the reference frame or restrictions apply in such a fashion that all the pixels needed for interpolation fall inside the reference frame.
Thank You
Chaitanya
-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/mp4-tech/attachments/20080528/fe43755c/attachment.html