Filmmaker agreed to give me music credits for using my music. Excerpts of film are on youtube .without credits. What can i do?

Assuming the YouTubed excerpts include your music, does your written contract specify that this use triggers their obligation to accord your music credit? It's possible that you could do a DMCA takedown notice for copyright infringement, but your goal is to get the proper credit up, and not to have to film excerpts taken down, so see a lawyer for help in drafting a demand letter.

Hopefully your agreement was in writing, as that will be much easier to enforce than any oral agreement. At any rate, you my have claims for breach of contract and/or copyright infringement, but that will depend on the specific terms of your agreement with the filmmaker. An experienced copyright attorney should be able to review your agreement and craft a suitable demand letter, hopefully resulting in the appropriate credit being given. In the event the filmmaker is not willing to cooperate, YouTube has standardized procedures for submitting copyright claims that may result in pulling down the video. While disabling access to the work might not be the end goal, it might be sufficient leverage to get the filmmaker to give you proper attribution.

Most YouTube posting allow for comments and have very few comments. Why not just post a comment with the credit line you want. Or, you might even post it several times if you want. Then see a copyright attorney to prepare a letter demanding they add a credit line with a threat of having the excerpts taken down if they down. Be prepared to follow through with the take down notice if you need. I think you likely just want the credit not the take down.

I think Ms. Koslyn identified the key issue: did the filmmaker agree to afford you credit on the YouTube usage. The credit provisions of a typical film deal include language like "Producer shall afford Composer credit on the Picture in the main titles on a single card in the following form [omitted].... All other characteristics of Composer's credit shall be in Producer's sole, absolute, and unfettered discretion." Sometimes the language includes the right to be included in paid ads (or all ads). Sometimes it has language that Composer will receive credit anytime the director, writer, principal cast members, or the like receive credit. Whether you have the right to be credited on the main titles, end titles, paid ads, trailers, or YouTube excerpts depends completely on the language of your credit provision. If you have no written agreement, and the filmmaker gave you credit on the film itself, it may be hard to prove that the filmmaker also was obligated to credit you on the YouTube clip. Composers/music licensors are often not included in the billing block of a picture. So, custom and practice in the industry would not be helpful evidence to establish that the failure to afford credit was a breach of contract or copyright infringement. Lastly, most production agreements have anti-injunction language that allow the artist to sue only for damages but disallow the artist from halting distribution/exploitation by means of an injunction or other equitable relief. If such language exists in your contract a DMCA takedown notice might be ineffective (depending on how broad the language in the provision is). This is an issue that really requires the attention of a local entertainment/copyright attorney.