Read data and append it to the current content of the AVPacket.
If pkt->size is 0 this is identical to av_get_packet.
Note that this uses av_grow_packet and thus involves a realloc
which is inefficient. Thus this function should only be used
when there is no reasonable way to know (an upper bound of)
the final size.
@param s associated IO context
@param pkt packet
@param size amount of data to read
@return >0 (read size) if OK, AVERROR_xxx otherwise, previous data
will not be lost even if an error occurs.
Read data and append it to the current content of the AVPacket. If pkt->size is 0 this is identical to av_get_packet. Note that this uses av_grow_packet and thus involves a realloc which is inefficient. Thus this function should only be used when there is no reasonable way to know (an upper bound of) the final size.
@param s associated IO context @param pkt packet @param size amount of data to read @return >0 (read size) if OK, AVERROR_xxx otherwise, previous data will not be lost even if an error occurs.