The subject is the 'setts' filter. The text below is my compact synopsis of section 2.27 of the
bitstream filters.
Below the text, please find 5 [question]s. Those are my questions, and I've been pondering them for
a long time, but any comments are very welcome of course.
Thanks for help -- much appreciated,
Mark.
2.27 setts -- Set target DTSs or PTSs or both.
'setts=dts=?' ...no defaults.
'setts=pts=?' ...no defaults.
'setts=ts?' ...alias for 'setts=pts=?'. [question 1]
'setts=dts=?:pts=?' ...no defaults.
: :
: eval API expression for target PTSs (plus the Factors below)
[question 2]
eval API expression for target DTSs (plus the Factors below)
[question 2]
Factors: For every 'current' frame, 'N', compute DTS and/or PTS using the
following factors:
'N' ...the frame number (i.e. 0 1 2..).
'TB' ...the current TB within the filter chain.
'STARTDTS' ...the DTS of source frame 0.
'PREV_INDTS' ...the DTS of source frame N-1.
'PREV_OUTDTS' ...the DTS of target frame N-1.
'DTS' ...the DTS of source frame N.
'STARTPTS' ...the PTS of source frame 0.
'PREV_INPTS' ...the PTS of source frame N-1.
'PREV_OUTPTS' ...the PTS of target frame N-1.
'PTS' ...the PTS of source frame N.
'TS' ...in 'dts=', the DTS of the current frame; in 'pts=', the PTS
of the current frame.
'POS' ...the original position in the file of the packet, or
'undefined' if undefined for
the current packet. [question 3]
'SR' ...The sample rate of stream packet belongs. [question 4]
'NOPTS' ...The AV_NOPTS_VALUE constant. [question 5]
[question 1] Is 'ts=' simply an alias for 'pts='?
[question 2] Regarding "The expressions are evaluated through the eval API", does that mean that all
of these: 'abs' 'acos' 'asin' .. 'time' 'trunc' 'while', are available? Or does it simply mean that
the expressions are evaluated by the eval API, but the eval AVI built-in factors are not necessarily
available?
[question 3] Regarding 'POS', is it some sort of packet index? Or sector number for disc-based
media? Or byte offset? Or something else? And of what utility is it?
[question 4] Regarding 'SR', besides referring to 'sample rate', what is it? Is it source fps? Or is
it something else?
[question 5] What does "AV_NOPTS_VALUE" do? Is it really 0x8000000000000000? What are the
implications? And what about this (from 2017): https://github.com/Ruslan-B/FFmpeg.AutoGen/issues/55?
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