[FFmpeg-devel] [PATCH] avfilter: add EIA-608 line extractor

[Paul B Mahol]

On 1/18/17, Tobias Rapp <t.rapp at noa-archive.com> wrote:
> On 17.01.2017 20:43, Paul B Mahol wrote:
>> Signed-off-by: Dave Rice <dave at dericed.com>
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  doc/filters.texi            |  70 ++++++++++++
>>  libavfilter/Makefile        |   1 +
>>  libavfilter/allfilters.c    |   1 +
>>  libavfilter/vf_readeia608.c | 268
>> ++++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 340 insertions(+)
>>  create mode 100644 libavfilter/vf_readeia608.c
>>
>> diff --git a/doc/filters.texi b/doc/filters.texi
>> index 94548b1..57170e3 100644
>> --- a/doc/filters.texi
>> +++ b/doc/filters.texi
>> @@ -11249,6 +11249,76 @@ less than @code{0}, the filter will try to use a
>> good random seed on a
>>  best effort basis.
>>  @end table
>>
>> + at section readeia608
>> +
>> +Read closed captioning (EIA-608) information from the top lines of a
>> video frame.
>> +
>> +This filter adds frame metadata for @code{lavfi.readeia608.cc.X} and
>> + at code{lavfi.readeia608.line.X}, where @code{X} is the number of the
>> identified line
>> +with EIA-608 data (starting from 0). A description of each metadata value
>> follows:
>> +
>> + at table @option
>> + at item lavfi.readeia608.cc.X
>> +The two bytes stored as EIA-608 data (printed in hexadecimal).
>> +
>> + at item lavfi.readeia608.line.X
>> +The number of the line on which the EIA-608 data was identified and read.
>> + at end table
>
>  From what I see this is a pair of values that belong together.
>
> lavfi.readeia608.X.cc
> lavfi.readeia608.X.line
>
> would indicate that better, IMHO.

Changed.

>
>> +
>> +This filter accepts the following options:
>> +
>> + at table @option
>> + at item start
>> +Set the line to start scanning for EIA-608 data. Default is @code{0}.
>> +
>> + at item end
>> +Set the line to end scanning for EIA-608 data. Default is @code{29}.
>
> What about naming them "scan_min/scan_max" for alignment with "readvitc"
> filter?

OK.

>
>> +
>> + at item mac
>> +Set minimal acceptable amplitude change for sync codes detection.
>> +Default is @code{0.2}. Allowed range is @code{[0.001 - 1]}.
>> +
>> + at item spw
>> +Set the ratio of width reserved for sync code detection.
>> +Default is @code{0.27}. Allowed range is @code{[0.01 - 0.7]}.
>> +
>> + at item mhd
>> +Set the max peaks height difference for sync code detection.
>> +Default is @code{0.1}. Allowed range is @code{[0.0 - 0.5]}.
>> +
>> + at item mpd
>> +Set max peaks period difference for sync code detection.
>> +Default is @code{0.1}. Allowed range is @code{[0.0 - 0.5]}.
>> +
>> + at item msd
>> +Set the first two max start code bits differences.
>> +Default is @code{0.02}. Allowed range is @code{[0.0 - 0.5]}.
>> +
>> + at item bhd
>> +Set the minimum ratio of bits height compared to 3rd start code bit.
>> +Default is @code{0.75}. Allowed range is @code{[0.01 - 1]}.
>> +
>> + at item wth
>> +Set the white color threshold. Default is @code{0.35}. Allowed range is
>> @code{[0.1 - 1]}.
>> +
>> + at item bth
>> +Set the black color threshold. Default is @code{0.15}. Allowed range is
>> @code{[0.0 - 0.5]}.
>
> "thr_w/thr_b"?

Could change...

>
>> +
>> + at item chp
>> +Enable checking the parity bit. In the event of a parity error, the
>> filter will output
>> + at code{0x00} for that character. Default is false.
>> + at end table
>> +
>> + at subsection Examples
>> +
>> + at itemize
>> + at item
>> +Output a csv with presentation time and the first two lines of identified
>> EIA-608 captioning data.
>> + at example
>> +ffprobe -f lavfi -i movie=captioned_video.mov,readeia608 -show_entries
>> frame=pkt_pts_time:frame_tags=lavfi.readeia608.cc.0,lavfi.readeia608.cc.1
>> -of csv
>> + at end example
>> + at end itemize
>> +
>>  @section readvitc
>>
>>  Read vertical interval timecode (VITC) information from the top lines of
>> a
>>
>> [...]
>
> BTW: Do you have some example file available for testing?

Yes, but I'm afraid I can not share them.

Here is one available:

https://archive.org/details/cc_sample