public InputStream recordInputStream(BufferSupplier bufferSupplier) {
        final ByteBuffer buffer = this.buffer.duplicate();
        buffer.position(RECORDS_OFFSET);
        return Compression.of(compressionType()).build().wrapForInput(buffer, magic(), bufferSupplier);
    }
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