Software Documentation

Time codeDocumentation

Last updated: January 3, 2019

2 Technical note: comparison of old and new Pyrodigital field controllers for SMPTE

Because some questions have arisen regarding the use of drop-frame SMPTE time code with Pyrodigital field controllers, we ran some tests to characterize their behavior.  The same set of tests was run on the original Field Controller and the new Field Controller A.

A series of 61 cues were programmed to ignite on consecutive frames, and were downloaded into two data tables.  Two versions were created:  one for drop-frame (DF) SMPTE and one for non-drop frame (NDF) SMPTE.  The sequence began at frame 00:00:59;00 in order to traverse the specific time of interest in drop-frame SMPTE.  With drop-frame SMPTE, frame numbers 00:01:00;00 and 00:01:00;01 are skipped in the frame-numbering scheme.  The data frames continue at a regular rate, just with those two frame numbers skipped in the frame header.  This repeats on one minute boundaries, except at multiples of 10 minutes.

The DF version of the data has no ignition cues on the dropped frame numbers, which are 00:01:00;00 and 00:01:00;01.  This corresponds with the fact that those frame numbers are not present in the DF SMPTE time code stream.  The NDF version of the data does not omit the frames noted above for DF.  It includes ignition cues assigned to all 30 frames in each second, corresponding to the presence of 30 frame numbers every second in the NDF SMPTE stream.

Each of these data tables was executed with a DF SMPTE stream, and a NDF SMPTE stream, for a total of 4 tests.  (The two cases where the format was mismatched were simply run out of curiosity, as they do not represent proper configurations.)  To determine which cues fired, immediately after a test was run, the data table was examined for the presence of a “*” on each cue line.  This indicates that the controller fired that specific cue line.  If a “*” was not present, that means that the controller did not attempt to fire the cue.

There was some uncertainty regarding the SMPTE configuration on the new Field Controller A, which presents the dialog shown in Figure 1 when SMPTE is selected in Auto Fire mode.

 

Figure 1 – Options presented by Field Controller A. Option 0 was selected for the test.

 

All tests were run on December 9, 2018. The results are shown in the following two tables for the original Field Controller and the new Field Controller A. Red indicates an incorrect result. Green indicates the desired result. Uncolored cells indicate no test was performed for those configurations.

 

Table 1 – Using original Field Controller, software version 3.00M (SMPTE co-processor version unknown)

Data Format
DF NDF
SMPTE Format 29.97 DF All cues fired except:
00:01:00;02 and 00:01:00;03
This is incorrect.  All should have fired except:
00:01:00;00 and 00:01:00;01
(format mismatch)
Not run on original Field Controller
30 NDF (format mismatch)
Not run on original Field Controller
All cues fired

 

Table 2 – Using new Field Controller “A”, software version 1.2.1 – 2018

Data Format
DF NDF
SMPTE Format 29.97 DF All cues fired (format mismatch)
All cues fired
30 NDF (format mismatch)
All cues fired
All cues fired

 

Of particular interest is the use of DF SMPTE with the original Field Controller, as it skipped the wrong data frames as it traversed the “drop frame” portion of the time code stream.  Previous tests indicated that this errant behavior is data-sensitive and can vary.  Care should be taken to avoid programming cues in the vicinity of the drop-frame regions if using DF SMPTE on the original controller.

The new Field Controller “A” fired all cues in all cases, even the mismatched case where DF SMPTE was used, and missing frame numbers were still fired from the data table.  This behavior builds confidence that all cues will fire when using SMPTE, even in the case of an inadvertent format mismatch.