Emojicode, 263 bytes

🏁🍇🔤🔤➡️🖍🆕s🔂b📇🆕🔡👂🏼❗️❗️🍇🍪s🔪🔡🔢b❗️➕128 2❗️1 7❗️🍪➡️🖍s🍉🔤?🔤➡️🖍🆕p🔂b s🍇↪️b����p🍇👄🔤0🔤❗️🍉🙅🍇👄🔤1🔤❗️🍉b➡️🖍p🍉🍉

Try it online here.

Ungolfed:

🏁 🍇  💭 Main code block
    🔤🔤 ➡️ 🖍 🆕 s  💭 Start with s as the empty string
    🔂 b 📇 🆕 🔡 👂🏼  💭 For each byte b in the input ...
    ❗️ ❗️ 🍇
        🍪 s  💭 ... append ...
           🔪 🔡 🔢 b ❗️ ➕ 128  💭 ... the b + 128 (this gives the leading zero(s) in case the binary representation of b is a shorter than 7 digits) ...

                 2  💭 ... in binary ...
              ❗️
              1 7  💭 ... without the leading one ...
           ❗️
        🍪
        ➡️ 🖍 s  💭 ... to s
    🍉
    🔤?🔤 ➡️ 🖍 🆕 p  💭 This will be used as the previous character, by assigning it neither 0 nor 1 we assure the first bit output is always a one
    🔂 b s 🍇  💭 For each character in s:
        ↪️ b 🙌 p 🍇  💭 If it is the same as the previous character ...
            👄 🔤0🔤 ❗️  💭 ... output a zero ...
        🍉 🙅 🍇  💭  ... else ...
            👄 🔤1🔤 ❗️ 💭 ... output a one
        🍉
        b ➡️ 🖍 p  💭 And the current character becomes the new previous character.
    🍉
🍉