Hi, On Wed, Feb 1, 2012 at 3:02 PM, Alex Converse <[email protected]> wrote: > On Wed, Feb 1, 2012 at 2:18 PM, Ronald S. Bultje <[email protected]> wrote: >> On Wed, Feb 1, 2012 at 1:26 PM, Alex Converse <[email protected]> >> wrote: >>> 2012/2/1 Måns Rullgård <[email protected]>: >>>> "Ronald S. Bultje" <[email protected]> writes: >>>> >>>>> Prevent values in floor1[] from wrapping over uint16_t boundaries (in >>>>> crafted bitstreams, they can go < 0), which causes them to wrap to >>>>> MAXUINT16, causing huge jumps in the dB LUT indexes. Likewise, clip >>>>> (rather than wrap) dB LUT indexes, to prevent jumping of indexes at >>>>> uint8_t wrapping boundaries. >>>> >>>> Why does it matter how invalid streams are decoded, as long as it >>>> doesn't crash or overrun buffers? >>>> >>> >>> Are large floor1 values actually forbidden? I've noticed that in both >>> Vorbis and AAC a lot of very stupid behavior is legal despite >>> increased decoder complexity to handle the behavior properly. >> >> The vorbis devs say my patch is correct. > > That's not what I asked.
They're not possible (at least not as large as MAXUINT16). The exact limit isn't implied in the spec, but the libvorbis encoder clips to 255 or 256, according to people in #vorbis. Other encoders (like ours) may not do so, so larger values may be used in practice and are certainly not in conflict with the spec, therefore clipping them at that level (255 or 256) isn't right in a decoder (since it'd break prediction of later values). Ronald _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
