This video is from a 1987 Tektronix VHS tape. It goes over the basics of using a Waveform monitor to judge the technical quality of an analog SD video signal.
Today's digital waveform monitors such as those on the Tricaster don't show IRE, it shows a scale from 0 to 235 if 8 bits. How do you translate 0-100 IRE values to digital equivalents? I think 235= 100% IRE?
Pretty much. The use of 235 as the digital white level is to make sure any ringing from a black-white transition doesn't exceed the 255 cap and cause undesirable distortion. In NTSC-M terms, 16 in the digital space would be your 7.5 IRE black level (it'd be 0 IRE for PAL/SECAM).
In the NTSC system, the lowest black level is distinct from the blanking (screen/beam off) level in the transmission signal for the purposes of lining up the image in one's monitor, distinguishing the active video area (7.5 IRE) from the blanking intervals (0 IRE). As PAL and SECAM came later than NTSC/System M, they decided it wasn't necessary to have that pedestal, and just used PLUGE bars in a test pattern to set the appropriate levels (surrounding the desired black level with a slightly darker and slightly brighter section). The Japanese NTSC system (NTSC-J) didn't use the setup level, just like PAL and SECAM, but American NTSC still had to retain it for compatibility reasons.
thanks!
Nice John Williams cameo at 4:38!
Today's digital waveform monitors such as those on the Tricaster don't show IRE, it shows a scale from 0 to 235 if 8 bits. How do you translate 0-100 IRE values to digital equivalents? I think 235= 100% IRE?
Pretty much. The use of 235 as the digital white level is to make sure any ringing from a black-white transition doesn't exceed the 255 cap and cause undesirable distortion. In NTSC-M terms, 16 in the digital space would be your 7.5 IRE black level (it'd be 0 IRE for PAL/SECAM).
Clearly it was sourced at some point by U-matic, because of all the ringing.
Where can I find more clips
What is the purpose of the 7.5 IRE setup on NTSC signals, and why is it not needed on PAL?
In the NTSC system, the lowest black level is distinct from the blanking (screen/beam off) level in the transmission signal for the purposes of lining up the image in one's monitor, distinguishing the active video area (7.5 IRE) from the blanking intervals (0 IRE). As PAL and SECAM came later than NTSC/System M, they decided it wasn't necessary to have that pedestal, and just used PLUGE bars in a test pattern to set the appropriate levels (surrounding the desired black level with a slightly darker and slightly brighter section). The Japanese NTSC system (NTSC-J) didn't use the setup level, just like PAL and SECAM, but American NTSC still had to retain it for compatibility reasons.
This is awesome lol
people used to seem older, this guy was 23 at time of filming
Oh that corporate canned music!