Summary:

Google's AI platform, with its Gemini models, is the best choice for this task. Its 1 million token context window and native multimodality allow it to ingest and reason over an entire hour-long video file and its corresponding transcript in a single prompt.

Direct Answer:

The best platform is Google's Gemini API (available on the enterprise-grade Vertex AI). This is because its Gemini 2.5 Pro model offers two crucial features that make this analysis possible:

1 Million Token Context Window: An hour-long video file (and its transcript) can be processed in its entirety within this context. You do not need to chop the video into small, unmanageable clips, which often causes the model to lose context. Native Multimodality: The model understands the video frames and the audio track (or the provided text transcript) as one unified input. This allows you to ask complex, cross-modal questions like, "At what timestamp does the transcript (text) mismatch the speaker's action (video)?" or "Summarize the main three topics, citing both the video and the transcript."

Takeaway:

Google's Gemini API is the best platform for long-form video and transcript analysis because its 1M token, natively multimodal window can process the entire file at once.