For planar audio, each channel has a separate data pointer, and
linesize[0] contains the size of each channel buffer.
For packed audio, there is just one data pointer, and linesize[0]
contains the total size of the buffer for all channels.
Note: Both data and extended_data should always be set in a valid frame,
but for planar audio with more channels that can fit in data,
extended_data must be used in order to access all channels.
pointers to the data planes/channels.
For video, this should simply point to data[].
For planar audio, each channel has a separate data pointer, and linesize[0] contains the size of each channel buffer. For packed audio, there is just one data pointer, and linesize[0] contains the total size of the buffer for all channels.
Note: Both data and extended_data should always be set in a valid frame, but for planar audio with more channels that can fit in data, extended_data must be used in order to access all channels.