ardour/livetrax
13
0
Fork 0
Code

Fix erractic timecode detection when extracting LTC from video

Browse Source 
Some music using square waves can inadvertently be interpreted as valid
LTC frame. However the encoded data is not a valid timecode, which can
lead huge A/V offsets, or other issues.
This commit is contained in:
Robin Gareus 2022-09-03 21:31:47 +02:00
parent 8af793a44d
commit 9697187037
3 changed files with 21 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
libs/ardour/ardour/ltc_file_reader.h
View File

@ -38,7 +38,7 @@ public:
void write (float const*, samplecnt_t n_samples, samplepos_t pos = -1);
void raw_write (ltcsnd_sample_t*, size_t, ltc_off_t);
samplepos_t read (uint32_t& hh, uint32_t& mm, uint32_t& ss, uint32_t& ff);
samplepos_t read (uint32_t& hh, uint32_t& mm, uint32_t& ss, uint32_t& ff, samplecnt_t& len);
private:
LTCDecoder* _decoder;
@ -79,6 +79,7 @@ private:
LTCReader* _reader;
float* _interleaved_audio_buffer;
samplecnt_t _samples_read;
float _apv;
};

22
libs/ardour/ltc_file_reader.cc
View File

@ -83,7 +83,7 @@ LTCReader::raw_write (ltcsnd_sample_t* buf, size_t size, ltc_off_t off)
}
samplepos_t
LTCReader::read (uint32_t& hh, uint32_t& mm, uint32_t& ss, uint32_t& ff)
LTCReader::read (uint32_t& hh, uint32_t& mm, uint32_t& ss, uint32_t& ff, samplecnt_t& ll)
{
LTCFrameExt ltc_frame;
if (0 == ltc_decoder_read (_decoder, &ltc_frame)) {
@ -96,6 +96,8 @@ LTCReader::read (uint32_t& hh, uint32_t& mm, uint32_t& ss, uint32_t& ff)
mm = stime.mins;
ss = stime.secs;
ff = stime.frame;
ll = ltc_frame.off_end - ltc_frame.off_start;
return ltc_frame.off_start;
}
@ -108,6 +110,7 @@ LTCFileReader::LTCFileReader (std::string path, double expected_fps, LTC_TV_STAN
, _reader (0)
, _interleaved_audio_buffer (0)
, _samples_read (0)
, _apv (1920)
{
memset (&_info, 0, sizeof (_info));
assert (Glib::file_test (_path, Glib::FILE_TEST_EXISTS));
@ -116,7 +119,7 @@ LTCFileReader::LTCFileReader (std::string path, double expected_fps, LTC_TV_STAN
throw failed_constructor ();
}
const int apv = rintf (_info.samplerate / _expected_fps);
_apv = _info.samplerate / _expected_fps;
#if 0 // TODO allow to auto-detect
if (expected_fps == 25.0) {
@ -129,7 +132,7 @@ LTCFileReader::LTCFileReader (std::string path, double expected_fps, LTC_TV_STAN
_ltc_tv_standard = LTC_TV_FILM_24;
}
#endif
_reader = new LTCReader (apv, _ltc_tv_standard);
_reader = new LTCReader (rintf (_apv), _ltc_tv_standard);
}
LTCFileReader::~LTCFileReader ()
@ -208,8 +211,19 @@ LTCFileReader::read_ltc (uint32_t channel, uint32_t max_frames)
Timecode::Time timecode (_expected_fps);
samplepos_t off_start;
samplecnt_t ltc_length;
while ((off_start = _reader->read (timecode.hours, timecode.minutes, timecode.seconds, timecode.frames, ltc_length)) >= 0) {
/* sanity check */
if (timecode.hours > 23 || timecode.minutes > 60 || timecode.seconds > 60) {
continue;
}
float speed = ltc_length / _apv;
if (speed > 5 || speed < 0.2) {
continue;
}
while ((off_start = _reader->read (timecode.hours, timecode.minutes, timecode.seconds, timecode.frames)) >= 0) {
int64_t sample = 0;
Timecode::timecode_to_sample (
timecode, sample, false, false,

2
share/scripts/ltc_reader.lua
View File

@ -28,7 +28,7 @@ function dsp_run (ins, outs, n_samples)
local rv
repeat
local tc
rv, tc = ltc_reader:read (0, 0, 0, 0)
rv, tc = ltc_reader:read (0, 0, 0, 0, 0)
if rv >= 0 then
timeout = 0
self:shmem():atomic_set_int (0, 1)