• Andreas Rheinhardt's avatar
    cbs: Don't set AVBuffer's opaque · 4e7e30bb
    Andreas Rheinhardt authored
    cbs is currently inconsistent regarding the opaque field that can be
    used as a special argument to av_buffer_create in order to be used
    during freeing the buffer: ff_cbs_alloc_unit_content and all the free
    functions used name this parameter as if it should contain a pointer to
    the unit whose content is about to be created; but both
    ff_cbs_alloc_unit_content as well as ff_cbs_h264_add_sei_message
    actually use a pointer to the CodedBitstreamContext as opaque. It should
    actually be neither, because it is unneeded (as is evidenced by the fact
    that none of the free functions use this pointer at all) and because it
    ties the unit's content to the lifetime of other objects, although a
    refcounted buffer is supposed to have its own lifetime that only ends
    when its reference count reaches zero. This problem manifests itself in
    the pointer becoming dangling.
    The pointer to the unit can become dangling if another unit is added to
    the fragment later as happens in the bitstream filters; in this case,
    the pointer can point to the wrong unit (if the fragment's unit array
    needn't be relocated) or it can point to where the array was earlier.
    It can also become dangling if the unit's content is meant to survive
    the resetting of the fragment it was originally read with. This applies
    to the extradata of H.264 and HEVC.
    The pointer to the context can become dangling if the context is closed
    before the content is freed. Although this doesn't seem to happen right
    now, it could happen, in particular if one uses different
    CodedBitstreamContexts for in- and output.
    Signed-off-by: 's avatarAndreas Rheinhardt <andreas.rheinhardt@gmail.com>
    4e7e30bb
cbs_vp9.c 19.8 KB