The same resolution as the FLV video — a 1080p FLV produces 1920×1080 TIFF frames; a 4K FLV produces 3840×2160 TIFF frames. Use the resize utility after extraction if you want smaller thumbnails or social-media-sized crops.
קען איך אױסשטעלן װײַל װיפֿל ראָמען פֿון FLV װי TIFF?
Almost always motion blur baked into the FLV source — the camera or subject was moving when the frame was captured. Pick timestamps from static scenes, or extract adjacent frames and choose the sharpest. The pipeline does not synthesize detail that was not there.