[FFmpeg-devel] [PATCH] Added integer 32 bits support to wavpack

[Reimar Döffinger]

On Sat, May 02, 2009 at 12:02:00AM +0530, Jai Menon wrote:
> On Fri, May 1, 2009 at 11:58 PM, Reimar D?ffinger
> <Reimar.Doeffinger at gmx.de> wrote:
> > On Fri, May 01, 2009 at 07:39:37PM +0300, Kostya wrote:
> >> On Fri, May 01, 2009 at 06:08:37PM +0200, Laurent Aimar wrote:
> >> > > I'd use s->crc_extra = AV_RL32(buf) and open bit buffer after that but this
> >> > > looks fine too. Oh, and please add block size check.
> >> > ?Using the bitstream reader here seems simpler to me, and additionnaly
> >> > avoid the need of buffer size checks ;)
> >>
> >> It's not - if size <=4 (as WavPack source code says), it should be treated as
> >> error, so check is needed anyway (not for bits reading though).
> >
> > Huh? Where does that idea that using the bitstream reader means you can
> > skip the size checks come from?
> > Is that why ALAC is so horribly broken in that regard?
> 
> Very likely. All input is done *solely* using get_bits, so adding
> checks requires some hacks.

I don't know what you consider hacks, but attached patch e.g. fixes
issue 758 (I sent it a long time ago to roundup and just tried again -
it still seems to refuse any mail with a patch).
The uncompressed case still needs to be fixed/optimized (and even the
compressed case could be improved) but I can't see what would be so
horrible about it that it would be better to have crashes.
Actually I don't consider it bad enough to explain why it wasn't done
in the first place.
-------------- next part --------------
Index: libavcodec/alac.c
===================================================================
--- libavcodec/alac.c	(revision 18377)
+++ libavcodec/alac.c	(working copy)
@@ -183,6 +183,9 @@
         /* standard rice encoding */
         int k; /* size of extra bits */
 
+        if (get_bits_count(&alac->gb) >= alac->gb.size_in_bits)
+            break;
+
         /* read k, that is bits as is */
         k = av_log2((history >> 9) + 3);
         x= decode_scalar(&alac->gb, k, rice_kmodifier, readsamplesize);
@@ -507,6 +510,8 @@
             av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
 
         for (chan = 0; chan < channels; chan++) {
+            if (get_bits_count(&alac->gb) >= alac->gb.size_in_bits)
+                break;
             bastardized_rice_decompress(alac,
                                         alac->predicterror_buffer[chan],
                                         outputsamples,
@@ -539,6 +544,8 @@
         /* not compressed, easy case */
         int i, chan;
         for (i = 0; i < outputsamples; i++)
+            if (get_bits_count(&alac->gb) >= alac->gb.size_in_bits)
+                break;
             for (chan = 0; chan < channels; chan++) {
                 int32_t audiobits;