@Override
            protected Record readNext(long baseOffset, long baseTimestamp, int baseSequence, Long logAppendTime) {
                try {
                    return DefaultRecord.readFrom(buffer, baseOffset, baseTimestamp, baseSequence, logAppendTime);
                } catch (BufferUnderflowException e) {
                    throw new InvalidRecordException("Incorrect declared batch size, premature EOF reached");
                }
            }
Gets the base timestamp of the batch which is used to calculate the record timestamps from the deltas.

@return The base timestamp
clients/src/main/java/org/apache/kafka/common/record/DefaultRecordBatch.java