I switched to J River for my OTA recording to replace Windows Media Center. It is working great, and saves the recording in the TS format, which I then use VideoReDo to remove commercials. I've been saving them into the same container (TS), but I have a problem with my Roku players. They play just fine, but I can't FF, rewind or resume from a TS container. No idea why, nor does the Roku programmer that works on their media player. If I save the recording to MKV, all trick play functions are available, but the EIA-608 caption tracks are not saved. I've also tried the MP4 container, but it appears that Roku players don't like MPEG2 video in an MP4 container. Even running FFMPEG from the command line in pure copy mode leaves the captions behind.
So, am I stuck with the TS container? I really don't want to change the codecs used, as that adds significantly more time to my commercial removal. If I leave the video and audio intact, it only takes about 45 seconds to save the edited video. Changing the video codec takes over 6 minutes for a 22 minute TV episode.
So, am I stuck with the TS container? I really don't want to change the codecs used, as that adds significantly more time to my commercial removal. If I leave the video and audio intact, it only takes about 45 seconds to save the edited video. Changing the video codec takes over 6 minutes for a 22 minute TV episode.
This essay is part of a larger research effort into the
original analog, Line-21/608 captioning systems.
Text and original artwork: Copyright © 2019 Art & Technic LLC
original analog, Line-21/608 captioning systems.
Text and original artwork: Copyright © 2019 Art & Technic LLC
Any chance you can also add the ability to insert captions (in EIA-608/708 form) as well? I'd like to be able to produce an mpeg2 ts which contains EIA-608/708 captions instead of having them burned into the video. FFMPEG didn't extract anything regardless of seeing the input track. Sample MOV available, but is 4.8GB and only 5mins long. Extract Eia-608 Captions Ffmpeg Avg 2018 Lisans Key Mirror For Samsung Tv License Key Mastering Qlik Sense Pdf Download How To Stop A Download Big Apple David Milch. Subtitles I want to convert to some other format, like subrip. On some movies this works, namely ones with 'movtext' subtitles. However some iTunes movies have eia608 subtitles which, when I try to convert them, throw this error: Closed caption Decoder @ 0000014b2b92eec0 Data Ignored since exceeding screen width. EIA-608, also known as 'line 21 captions' and 'CEA-608', was once the standard for closed captioning for NTSC TV broadcasts in the United States, Canada and Mexico. It also specifies an 'Extended Data Service', which is a means for including a VCR control service with an electronic program guide for NTSC transmissions that operates on the even line 21 field, similar to the TeleText based VPS.
Introduction
Closed Captioning is the original user-facing metadata ofbroadcast television.
It was designed - specifically and deliberately - to openthe audio-visual medium of television up to the deaf. With what wouldeponymously become known as “the decoder,” television slowly began tobecome accessible to the deaf, the hard-of-hearing, and in time (after beingmandated by law), the general public. The end product of decades ofadvocacy was simple, and yet profound: everyone could understand themeaning of television’s images in almost any environment.
In the 21st century, the wide availability ofcaptioning is taken for granted, as though it were a given. In this, as in mostthings, complacency is the enemy of progress. We should remember that the pathto the convenient, (seemingly) accessible present that we live in was, in fact,a hard-fought battle… that literally took decades.
In that light, it’s an easily made point that those who are chargedwith both preserving and making available the audio-visual materials of the past,should also make the effort to preserve – and make available – theprogram-related captioning that originally accompanied it.
In well-equipped post-production environments, there are avariety of means – inclusive of specialized hardware – which allow one to extract,encapsulate, and otherwise integrate the original caption data with the content.For those institutions and individuals who are preserving our audio-visualhistory on their own, outside the scope of those post-production facilities, budgets– and options – tend to be far more restrictive.
In that milieu, captioning all too frequently seems to be anoverlooked step-child. This is despite the fact that in the captioning schemeof things, a small amount of effort can go a long way in preservingthe accessibility of one’s collections. So, if budgets are truly anobstacle to maintaining their accessibility, could the root difficultyin doing so simply be a matter of tooling? After all, while the extraction of analogLine-21/608 caption data from digitized video is conceptually simple, on apractical basis, it can often be considerably more involved.
This is particularly true with respect to open-sourcesolutions. In our research, we discovered that there aren’t a bevy of optionsthat could be described as either “fit for purpose” or “ready to run.” In fact,both of the open-source packages that we’re aware of can be readily describedas “problematic,” each with their own unique set of complications.
The first of the two solutions that we discovered is, infact, quite noteworthy: it’s the only open-source program fully dedicated toperforming Line-21/608 caption data extraction from analog materials. While thisunnamed (for now) program does “work,” it is hardly fit for use withoutsignificant end-user effort. A small list of out-of-the-box issues:
- The program’s source code isn’t wholly portable, which in practicalterms means that it won’t run on the Macintosh platform without modifications tothe source code. This means that, for all intents and purposes, you have tohave some type of programming background to even hope to make use of thesoftware.
- Several basic aspects / functions of the program are either implementedincorrectly or are implemented in non-functional form.
- It is not designed for piped output in thenormal sense (requiring code modifications to do so).
- As a result of design decisions, the program has difficulty reading captioned material broadcast by the ABC television network between the years 1980 and 1992. (This is a grievous failure, given that ABC was an early champion of closed captioning.)
- In default operation, it doesn’t separate field one and field two data,which is highly problematic.
FFmpeg, the well-known hydra of the open-source world, isthe second open-source program that performs Line-21/608 caption dataextraction. In FFmpeg’s case, its support for Line-21/608 extraction comes entirelyby way of the readeia608filter. While this solution is more likely to run after downloading, as comparedto the previous program, it also has a set of provisos[1]:
- The author[s] appear[s] to be unfamiliar with the CEA/EIA 608specification, and how decoding is supposed to be carried out.
- The overall design of the decoding solution used in readeia608 issimultaneously novel and.. “interesting.” It appears to be based on a series of unstatedassumptions about the structure of the signal that they expect as input,instead of actually parsing the signal, per se. That the code is basedon these assumptions is semi-obfuscated, but clearly seen once one examines therole of the explicitly defined constants, as well as the defaults for several variables..which are effectively constants.[2]
- As a result of those design decisions, the filter may:
- Fail to decode or partially decode (distressed) Line-21 data
- Fail to decode Line-21 materials with a non-standard “clock”[3]
- Readily produce incorrectly decoded 608 data.
- The output format of the data – a dyad of hexadecimal values – is significantly less than ideal.[4]
From these two programs, we can only conclude – sadly – that with respect to analog Line- 21/608, the available open-source software packages both fall into the same trap: they’re both firmly in the category of “not-quite-working,” and therefore not-quite-fit for either the reliable extraction and/or preservation of Line-21/608 data. The underlying cause in both cases is seemingly less a matter of technical acumen, than one of conceptual understanding. This knowledge gap, as we’ve noted, is self-apparent from the code on both of these projects.
Microsoft access 2016 for mac free full version. Does this knowledge gap arise from open-source’s traditionalrecalcitrance to pay for widely available standards documents, which wouldprovide the knowledge that would serve as the basis for all future correct implementations?[5]Which is reflected in the open-source encyclopedia’s dumpsterfire of an entry on CEA/EIA-608?[6]Or, in this particular case, does it arise from the murky technical history ofclosed captioning, in which widely cited, fundamental historical documents concerningthe system seem to have vanished without a trace?[7]
The true answer is likely ‘a little from Column A, and alittle from Column B.’ Line-21/608 caption decoding is a matter of ‘art,’ inthe ancient sense of the word. When the craftsperson is unfamiliar with the art,the work product reflects that.[8]
As such, our purpose here is to lay the framework forcorrect future implementations… by way of education. Having implemented severalLine-21/608 data extraction routines in software, we not only know it can bedone, but that it can be done better. We hope that this article will aid othersin the correct implementation of their own extraction routines, so that theymay become the standard… and not the exception.
Contents
- The Line-21 Waveform: Background and Theory
- Data in the Line-21 Closed Captioning System
- Working with the Digitized Line-21 Waveform in Practice
- Data Extraction
The Line-21 Waveform: Background and Theory
The Line-21 waveform did not spring forth, fully formed,from the foreheads of either PBS or NCI in 1980. The Line-21 waveform[9],as we know it, was in fact the third iteration of a signal originally developedby the National Bureau of Standards[10]in the late 1960s.. for the dissemination of highly accurate reference time and frequencysignals on commercial television broadcasts.[11]It’s important to understand this, because the basic principles of decoding theLine-21 closed captioning signal rest with both the original design and purposeof that signal.
The original version of the Line-21 signal, as presented tothe FCC in 1973, looked like this:
As illustrated above, this signal was comprised of two major components:
- An analog 1 MHz frequency reference
- A 26-bit digital data transmission
The 1 MHz frequency reference portion of the signal was, literally,that: a reference 1 MHz signal generated by an NBS atomic clock, located at thepoint of origination, on the premises of the broadcaster. That 1 MHz frequency reference,however, did more than provide the entire nation with a federally traceablefrequency standard: it served as the “clock” for thedigital data portion of the transmission.
In a “decoder” of that era, the 1 MHz frequency burst was usedto excite a tank circuit.Once excited, the tank circuit’s output would then be used as a clock generator to decodethe digital data portion of the signal, which was encoded using Non-Return-to-Zero (NRZ)modulation.[12]
Important points to remember about the 1 MHz frequency reference:
- The 1 MHz burst was effectively the “clock” for the digital data portion of the signal.
- Without the “clock,” it would be 'impossible' to decode the digital data.
- As a result, the signal is, in a sense, self-describing: everything you need to correctly decode the signal is carried within the signal itself.
- Since the 1 MHz frequency reference was generated by an atomic clock, whose phase was independent of the video signal, it was not phasecoherent with the video signal.[13]
For a variety of reasons, the National Bureau of Standards’ Line-21system never gained approval from the FCC. However, PBS – who picked up the technologyfrom NBS – did receive a temporary authorization from the FCC to use a modifiedversion of the NBS system. That “interim” system was then used to develop the versionof the closed captioning system which debuted in 1980.[14]
That final version of the Line-21 signal, as presented to the FCC in 1976, looked like this:
Schematically, this incarnation is extremely similar to the NBSversion of the Line-21 signal. The primary differences that we can readily see arethat:
- The 1 MHz frequency reference has been replaced by a burst of a 503 kHz “clock run-in”
- The length of the “clock” has decreased
- The length of the digital data portion has increased
- The number of bits in the digital data transmission has been decreased to 16-bits
Although it may be difficult to discern on the face of things, each of these thingsare fundamentally interrelated.
How so? Well, let’s think back to the original version ofthe Line-21 signal: it was comprised of two discrete components. The first – a 1MHz frequency reference, which was taken from an external atomic clock – wasrequired to decode the second portion, the 26-bits of digital data. Since NBS designedthe signal to convey both highly accurate, standards-grade time and frequency referencesignals, it made sense to tie both of these elements together in that way.
PBS, however, did not have the dissemination of reference-gradetime and frequency signals in their mandate. What was in PBS’ mandate waspublic service – and PBS felt that making television accessible to theDeaf community was an important part of their nascent[15]network’s mission. As such, their version of the Line-21 signal needed to be centeredaround the television signal it would be ‘piggybacking’ on.
That change in “clock” frequency from 1 MHz to 503 kHz,therefore, reflected the change in the sponsoring agency’s mission: it is equivalentto analog NTSC’s horizontal line frequency, multiplied by 32. So, by basing the“clock” on the horizontal line frequency, the “clock” – and the remainder ofthe Line-21 signal, whose timing is based upon that clock – are consistentlyphase coherent with the analog video signal on which they are transmitted. Inother words, PBS’s Line-21 signal was designed to be a well-tempered videosignal that wouldn’t wobble horizontally, unlike the NBS signal.[16]
Another consequence of reducing the frequency of the clock isthat the clock’s ‘interval’ increases.[17]Put differently: this means that in PBS’ version of the Line-21 signal, a ‘bit’is nearly twice as wide as a ‘bit’ in the original NBS system. Which, in turn, explainswhy there’s less real-estate available for the clock, and more dedicated to thedata: the 16-bits of digital data that are transmitted in the PBS system requiremore real-estate.. because the individual bits are ‘wider.’
Data in the Line-21 Closed Captioning System
The doubling in size of each individual ‘bit,’ and thereduction in the number of transmitted bits per frame were both purposefuldesign choices. PBS did this to ensure that the captioning data could besuccessfully decoded even if the reception of the channel it was transmitted onwas less than ideal.[18]Therefore, the ability to recover and decode captioning data from less thanideal signals was a design decisionfortheirclosedcaptioning system.
(This is a critical point, which we cannot emphasize enough:this system was designed from the bottom-up to work in aparticular way to reach those design goals. From the structure of the PBSLine-21 signal, to the code structure of the encapsulated data, to themethodology of data extraction, and to how a ‘decoder’ displays that extracted dataon a screen, the design decisions are all part of a coherent system that takesinto account the medium on which it was conveyed. Correctly handlingLine-21/608 data is, therefore, a matter of correctly emulating theoperation of a physical decoder.)
The fundamental way in which PBS’ Line-21 signal differsfrom the NBS system is that the data ‘bit’ – whose size is derived from theclock – structures the entire layout of the Line-21 signal. While the NBSLine-21 system specified a gap between the clock and the data, in the PBSsystem, the data portion of the signal begins at the end of the ‘clock.’ The physicalposition of every subsequent bit, therefore, is explicitly defined in terms ofhow many ‘bits’ they are from that starting point. The following diagram – froman Evertz equipment manual – illustrates this:
![Extract Eia 608 Captions Ffmpeg Extract Eia 608 Captions Ffmpeg](https://i.ytimg.com/vi/1WhMEWIb2S4/maxresdefault.jpg)
As we can see, starting immediately at the conclusion of the‘clock’ are three start bits, which are then followed by the payload of 16 databits. The payload is structured as a serial data transmission: a 7-bit ASCIIcharacter, and corresponding parity bit, followed by another 7-bit ASCIIcharacter, and its corresponding parity bit. The byte order of the transmissionis in keeping with the ASCII standard for serial transmission: Least-Significant-Bitfirst.[19]
If you were wondering how exactly a Line-21 decoder woulddetermine the point at which the clock signal ends, and the data portion begins,that’s because it’s not entirely obvious from the documents these diagrams weretaken from. In fact, it takes three pieces of information to discern:
- As denoted in both NBS and PBS Line-21 signal diagrams, the “center” ofthe waveform is at 25 IRE (50% maximum amplitude of the signal).
- From note 5 on PBS’ Line-21 signal diagram, “Negative going zero crossings of clock are coherent with data transitions.”
- And finally, from an early revision of EIA/CEA-608: “All interval measurements are made from the midpoints (half amplitude) on all edges.”
Taken together, we can conclude that a decoder “knows” thatit has reached the transition point between the ‘clock’ and data portions ofthe signal when:
- It has passed the seven peaks of the 503 kHz “clock run-in.”
- The amplitude of the last downward (negative) going portion of the clock signal is equivalent to 25 IRE (50% maximum amplitude of the signal).
If we were to look for that point on the above diagram, itwould be at the exact intersection of the 25 IRE level, and the rightmost,downward edge of the clock signal.
Working with the Digitized Line-21 Waveform inPractice
To extract closed captioned data as part of a post-captureworkflow, the source analog video needs to be digitized at the 720x486resolution. Digitization at the lower vertical resolution of 480 will likely resultin the Line-21 captioning data being cropped out during capture. Which,obviously, is a non-starter.
While the 720x486 resolution is sufficient for reproducingstandard definition imagery, it’s somewhat less than ideal when processing Line-21closed captioning signals. Practically speaking, this doesn’t mean thatdigitization precludes post-capture data extraction. Rather, it requires that onebe mindful of the limitations of the ‘sampling rate’ when designing anextraction algorithm.
A Line-21 data extraction algorithm should, in normaloperation, only require one input parameter: the video line in the source videofile that it should attempt to extract data from. In this sense, the algorithmshould (essentially) emulate the data extraction function of a physicalclosed-captioning ‘decoder.’ If a stand-alone piece of hardware can perform thesame function without a series of parameters from the user, then neither shouldyour algorithm.
Only in more involved data recovery operations – such asthat from marginal, distorted, or otherwise damaged sources – should a dataextraction algorithm require operational parameters from the user. For thosecircumstances, the basic set of optional parameters should be:
- Source video line for data extraction
- Clock-Width value[21]
- Threshold value for NRZ decoding[22]
- The Clock Must Be “Solved” for Each and Every Line
Although we’re going to delve into the why behind this in the following section, it bears mentioning here sinceit is singularly important. While solutions that approach the problem inalternative ways may “work,” they often do not work consistently, orconsistently well.
- The Clock ‘Interval’ is NOT an Integer
As noted elsewhere, thevalue of the clock ‘interval’ is a floating-point number. Your pixel samples,however, are an array of discrete (rectangular) samples.. which may or may notbe wholly coincident with the sampled Line-21 signal. You need to account forthis.
Data Extraction
As a process, data extraction is fairly straightforward. On a per line basis, one must:
- Solve for the clock
- Determine the location of the “bit zones”
- Perform NRZ decoding of each “bit zone”
- Return the parity checked value of each transmitted character
Since the clock is the critical element in discerning thelocation of each subsequent bit in the signal, you must determine a solutionfor the clock on every line. With the analog Line-21 signal, one must nottake for granted that all elements of the signal will consistently appear atthe same position on the line, every time. Frequently, as a result of normalvariation, time-base errors, reception issues, and even variations between elementsin the original post-production process, consistent timing (read: horizontal positioning)of the Line-21 signal is not guaranteed.
Take for instance the educational television series, The Voyage of the Mimi.Each episode in the series was comprised of two parts: part “A,” which was adramatic, fictionalized adventure, and part “B,” an educational ‘adventure’ thatdelved into some aspect of the science seen in the first half of the show. Thesetwo parts were each edited and captioned independently, and once finished, theywere edited together onto a single master videotape.
The relevance of the show’s post-production process tocaption data extraction is that at the join between part A and B, there is anobservable change in the positioning (timing) of the Line-21 signal. We can seethis readily in the waterfall / ‘overhead view’ of the Line-21 signal fromepisode seven:
While this timing change wouldn’t trip up a hardware decoder,for a software decoder that doesn’t appropriately solve for the clock… itcertainly would.
Regardless, once you’ve solved for the ‘clock,’ you can thenproceed to determine the location of the sixteen “bit zones.” A “bit zone,”strictly speaking, is the portion of the Line-21 real-estate that correspondsto a specific bit of data. The following diagram illustrates the location ofthe sixteen “bit zones” for a sample Line-21 signal:
To discern the value of a single bit, one must sum the valueof all pixels in that “bit zone,” and then divide that sum by the number ofsamples, to determine the average pixel value. If the calculated average pixelvalue is nominally greater-than-or-equal-to 50% of the maximum amplitude of theclock, the value of the bit is 1.[23]Otherwise, the value of the bit is 0.
Discerning the value of a bit in a “bit zone” in this way isan intentional part of the design of the Line-21 / 608 system: it aids datarecovery in difficult reception environments (noise, multipath, etc.),making the system more robust.
To decode each character, we must first discern thevalue of all bits for that character – inclusive of the parity bit. We mustthen check the value of the extracted character with respect to odd parity.If the character passes the parity check, we can then return the value of the extractedcharacter as-is. If the character does not pass the parity check, then thedecoded value is invalid, and we must instead return the value whichsignals this condition for a[n] Line-21/608 decoder.[24]
While it may be “easy” to ignore the parity bit, doing so isnot inconsequential: it produces a non-compliant data stream. A non-compliantdata stream, in turn, will likely result in unexpected behavior from compliantLine-21/608 decoders. So, to be compliant, one MUST check parity, and oneMUST return appropriate decoded values. Checking parity is NOToptional – it is mandatory by default.[25]
Coda
In this essay, we delved into the history and theory of theanalog Line-21/608 signal to illustrate the concepts underlying the operationof the system, and how data is to be correctly decoded for that system. Thisshould allow any programmer conversant in the ‘art’ to generate compliant decodingsolutions for caption data originating from analog sources.
We sincerely hope that this will be of help to those organizations,institutions, and individuals charged with preservation of the audio-visualmaterials of the past, and will help make these recordings – inclusive of thecaptioning data locked within them – more easily accessible to futuregenerations.
-DW
November 2019
(Slight revisions: December 2019)
November 2019
(Slight revisions: December 2019)
[1]We were unable to ascertain if the Line-21/608 extraction aspect works at all,as the filter wasn’t able to decode data from a test sample (an aircheck fromthe ABC television network in the mid-1980s), using the provided sample commandin the documentation. Therefore, all conclusions in this section are based upona close reading of the source code.
[2]Had the author[s] documented their code, this would have been clearer. If theauthor[s] believe that I am mischaracterizing their code, I would suggest addingboth COMMENTS and DOCUMENTATION to clarify both the operation of the code aswell as their design intentions.
[3]In all fairness, this is not an issue unique to this decoder, but worth notingnonetheless.
[4]In a follow-up essay, we propose a superior format for Line-21/608encapsulation: tabraw.
[5]In one discussion, someone involved in the open-source movement made an incredibleargument against paying for a copy of a standard: they’d much rather spend theirmoney with the Dollar Shave Club. While we can all agree that personal hygieneis important, so is professional competence and credibility. Ultimately,arguments against professional competence, credibility, and concomitant standardsare symptoms of institutional and/or intellectual poverty.
[6]At the time of writing, it was not only awfully written but, in many respects,dead wrong. Those seeking to learn about the standard are better served… by literallyany other reputable source.
[7]Art & Technic LLC is working to ameliorate this problem, both in thisdocument, and in other forthcoming projects.
[9]So named because the waveform occupies the entirety of Line 21 in analog NTSC video.
[10]The National Bureau of Standards (NBS) is better known today as the National Instituteof Standards and Technology (NIST).
[11]As summarized from ongoing research; subject to revision.
[12]The specific method used, as described by the Wikipedia, was ‘Unipolarnon-return-to-zero level’ modulation. It’s also individually discussed on itsown Wikipedia page: Unipolarencoding.
[13]While phase coherence is important to keep in mind for reasons that will soonbecome clear, the original system’s lack of phase coherence, and theimpact of that design decision in the original system, is not relevant to thescope of this article. This summary of the original system is derived fromongoing research; subject to revision.
[14]As summarized from ongoing research; subject to revision.
[15]Per the Wikipedia, PBS began operations on October 5, 1970.
![Extract eia 608 captions ffmpeg free Extract eia 608 captions ffmpeg free](https://digitensionshome.files.wordpress.com/2020/01/screen-shot-2020-01-13-at-15.32.19.png?w=407&h=230)
[16]The NBS system, whose frequency reference (“clock”) was taken from an atomicclock that had no phase relationship to the video signal on which it waspiggybacking, exhibited continuous timing ‘jitter’… because the instantaneousphase of the clock differed every 1/30th of a second. As aconsequence, the horizontal placement of the digital code transmission wouldvary from field to field as the phase of the “clock” varied with respect to thevideo signal. Visually, PBS’ system is a stark contrast with itspredecessor. Since the clock in the PBS system is phase coherent with the videosignal, that means that the position of each element in the signal – all ofwhich are based on the timing of the clock (which is in turn based on thetiming of the video signal itself) – consistently appear at consistent points. So,while PBS’ Line-21 system appears to be a largely static signal on a waveformmonitor, it actually is more involved behind-the-scenes. (The detail on the original system is derived fromongoing research; subject to revision.)
[17]When we say ‘interval’ here, we are referring to the “data bit interval” - thewidth of a single bit at that clock frequency. Per EIA/CEA-608, the width ofthat interval is defined as 1/(fH x 32), or in terms of time, 1.986µS.
[18]In the modern ATSC digital television system, reception is either good enoughto reproduce the transport stream, or not. Poor signal strength and multipathcan easily preclude successful reception of ATSC. In contrast, an analog NTSCreceiver could often provide a “watchable” signal in conditions that rangedfrom poor to marginal. (Development detail derived from ongoing research;subject to revision.)
[19]See Mackenzie, Charles, “Coded Character Sets, History and Development,” Addison-Wesley,1980, page 253. This chapter of the book – “Which Bit First?” – is concernedwith how the LSB / Little Endian standard for serial transmission of ASCII datacame about.. which also happens to be a brisk, informative, and worthwhile read.
[20]See EIA/CEA-608-B, October 2000, page 11, note 1.
[21]This is largely superfluous, because in the PBS Line-21 system, the clock-widthis literally a constant. (Remember: the clock ‘interval’ is based on thehorizontal line frequency of the television signal itself.)
Eia 608 Standard
[22]The basic principles of NRZ decoding with respect to Line-21 signals will bediscussed in the next section.
[23]Recall from earlier that 1) the center of the waveform is at 50% maximumamplitude of the clock, and that 2) all interval measurements are also made at half-amplitude.While there are a variety of ways to determine the threshold value when decodingLine-21 signals, this is the recommended starting point.
Extract Eia 608 Captions Ffmpeg File
[24]Nominally 7F hexadecimal. One should note that the process of data extractionis heavily tied into the operation of the decoder / display. See U.S. FederalRegister, Volume 56, Number 114, June 13, 1991, pages 27204-27205.
Extract Eia 608 Captions Ffmpeg Video
[25]While we can imagine some cases in which one may want an extractionroutine to return invalid values, this is a specialized use-case in datarecovery, and therefore should require an explicit option to turn parity offfor that explicit purpose.