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authorAndreas Rheinhardt <andreas.rheinhardt@gmail.com>2020-08-29 16:12:05 +0200
committerAndreas Rheinhardt <andreas.rheinhardt@gmail.com>2020-08-30 03:02:13 +0200
commit0166b1d1a6d052ef49aba3523d64f3c6d4f26372 (patch)
treedd6c361d1a553531edb85c1b4a16cc3c488f1165 /libavfilter/setpts.c
parent7c8cf40adcee516caaa16e7da364c87b204d31a6 (diff)
downloadffmpeg-0166b1d1a6d052ef49aba3523d64f3c6d4f26372.tar.gz
avcodec/wnv1: Use LE bitstream reader, avoid copying packet, fix memleak
The Winnov WNV1 format is designed for a little-endian bitstream reader; yet our decoder reversed every byte bitwise (in a buffer only allocated for this purpose) to use a big-endian bitstream reader. This commit stops this. Two things needed to be done to achieve this: The codes in the table used to initialize a VLC reader needed to be reversed bitwise (when initializing a VLC in LE mode, it is expected that the first bit to be read is in the least significant bit; with BE codes the first bit to be read is the most significant bit of the code) and the following expression needed to be adapted: ff_reverse[get_bits(&w->gb, 8 - w->shift)] But this is easy: When only the bits read are reversed, they coincide with what a little-endian bitstream reader reads that reads the original, not-reversed data. But ff_reverse always reverses the full eight bits and this also performs a shift by (8 - (8 - w->shift)) on top of reversing the bits read. So the above line needs to be changed to get_bits(&w->gb, 8 - w->shift) << w->shift and this also shows why the variable shift is named the way it is. Finally, this also fixes a hypothetical memleak: For gigantic packets, initializing a GetBitContext can fail and in this case, the buffer containing the reversed data would leak. Reviewed-by: Paul B Mahol <onemda@gmail.com> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Diffstat (limited to 'libavfilter/setpts.c')
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