Always consider m4a files as audio, even when they contain a video track.

        }

        public void setMimeType(String mimeType) {

            if ("audio/mp4".equals(mMimeType) &&

                    mimeType.startsWith("video")) {

                // for feature parity with Donut, we force m4a files to keep the

                // audio/mp4 mimetype, even if they are really "enhanced podcasts"

                // with a video track

                return;

            }

            mMimeType = mimeType;

            mFileType = MediaFile.getFileTypeForMimeType(mimeType);

        }