Complex sentence: SMPTE standardized the format within ITU-R 601, also known as Rec.601, which was derived from SMPTE 125M and EBU 3246-E standards.
Split into simpler sentences: SMPTE standardized the format within ITU-R 601, also known as Rec.601. The SMPTE ITU-R 601 standard was derived from SMPTE 125M and EBU 3246-E standards.