right above there is if (pkt) {<do stuff>; pkt = NULL}, so pkt is just a
fancy name for NULL at this point.

It has been disabled since it was added two years ago.

This location contains prebuilt binaries as well.
Signed-off-by: Martin Storsjö <martin@martin.st>

Same fix and issue as in a25d912dSigned-off-by: Anton Khirnov <anton@khirnov.net>

channels, sample_rate, bit_rate, and block_align can be used directly from
the AVCodecContext

A large invalid value could cause undefined behavior when left-shifted
by 8 later in the function.

This could occur due to integer overflow when reading the channel count from
the extradata.

Only mono 8kHz is supported.

Only mono 8kHz is supported.

For decoding it does not really matter what the sample rate is.

Although the libFLAC decoder cannot handle such a change, it is allowed by the
spec and could potentially occur with live streams.

Also, return an error on allocation failure.