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avutil/timecode: add description for SMPTE binary format

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Signed-off-by: Limin Wang <lance.lmwang@gmail.com>
This commit is contained in:
Limin Wang 2020-06-30 23:22:58 +08:00
parent 05f3d37dd5
commit c24c6a1bee
2 changed files with 15 additions and 2 deletions
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4
libavutil/frame.h
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@ -162,8 +162,8 @@ enum AVFrameSideDataType {
/**
* Timecode which conforms to SMPTE ST 12-1. The data is an array of 4 uint32_t
* where the first uint32_t describes how many (1-3) of the other timecodes are used.
* The timecode format is described in the av_timecode_get_smpte_from_framenum()
* function in libavutil/timecode.c.
* The timecode format is described in the documentation of av_timecode_get_smpte_from_framenum()
* function in libavutil/timecode.h.
*/
AV_FRAME_DATA_S12M_TIMECODE,

13
libavutil/timecode.h
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@ -62,6 +62,19 @@ int av_timecode_adjust_ntsc_framenum2(int framenum, int fps);
* @param framenum frame number
* @return the SMPTE binary representation
*
* See SMPTE ST 314M-2005 Sec 4.4.2.2.1 "Time code pack (TC)"
* the format description as follows:
* bits 0-5: hours, in BCD(6bits)
* bits 6: BGF1
* bits 7: BGF2 (NTSC) or PC (PAL)
* bits 8-14: minutes, in BCD(7bits)
* bits 15: BGF0 (NTSC) or BGF2 (PAL)
* bits 16-22: seconds, in BCD(7bits)
* bits 23: PC (NTSC) or BGF0 (PAL)
* bits 24-29: frames, in BCD(6bits)
* bits 30: drop frame flag (0: non drop, 1: drop)
* bits 31: color frame flag (0: unsync mode, 1: sync mode)
* @note BCD numbers (6 or 7 bits): 4 or 5 lower bits for units, 2 higher bits for tens.
* @note Frame number adjustment is automatically done in case of drop timecode,
* you do NOT have to call av_timecode_adjust_ntsc_framenum2().
* @note The frame number is relative to tc->start.