[FFmpeg-cvslog] af_pan: comment a tricky piece of code.

[Reimar Döffinger]

On Wed, Feb 15, 2012 at 08:12:36PM +0100, Nicolas George wrote:
> +        /* reject layouts that are not a single channel */
>          if (channel_id >= MAX_CHANNELS || layout0 != (int64_t)1 << channel_id)

If we ever used all 64 bits, (int64_t)1 << channel_id would actually be
a signed overflow.
Also 1ull is generally accepted as a shorthand I think (even though
the more proper one is UINT64_C(1) ).