[FFmpeg-devel] Fwd: libavformat/segment : add option to increment timecode

[Stefano Sabatini]

On date Friday 2016-01-29 12:18:02 +0100, Martin Vignali encoded:
> Ping
> 
> ---------- Forwarded message ----------
> From: Martin Vignali <martin.vignali at gmail.com>
> Date: 2015-10-03 15:49 GMT+02:00
> Subject: libavformat/segment : add option to increment timecode
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> 
> 
> Hello,
> 
> in attach a patch, who add an option to increment timecode using segment.
> 
> To test :
> 
> ffmpeg -i src.mov -timecode 10:00:00:00 -vcodec copy -f segment
> -segment_time 2 -reset_timestamps 1 -increment_tc 1 target_%03d.mov
> 
> the second file have timecode 10:00:02:00 (after the patch)
> instead of 10:00:00:00 (before the patch)
> 
> 
> This patch is useful for two kind of uses :
> - splitting a file, but keeping timecode of each part
> - have a continuous timecode when recording a stream using segment.
> 
> 
> Comments welcome.
> 
> Martin

> From e53698b08211a818e1fe924a532e142bbb64fc87 Mon Sep 17 00:00:00 2001
> From: Martin Vignali <martin.vignali at gmail.com>
> Date: Sat, 3 Oct 2015 15:39:41 +0200
> Subject: [PATCH] add increment timecode option using segment.
> 
> ---
>  libavformat/segment.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)

Please add docs in doc/muxers.texi.
 
> diff --git a/libavformat/segment.c b/libavformat/segment.c
> index 36417f2..f3e1ab3 100644
> --- a/libavformat/segment.c
> +++ b/libavformat/segment.c
> @@ -40,6 +40,7 @@
>  #include "libavutil/parseutils.h"
>  #include "libavutil/mathematics.h"
>  #include "libavutil/time.h"
> +#include "libavutil/timecode.h"
>  #include "libavutil/time_internal.h"
>  #include "libavutil/timestamp.h"
>  
> @@ -92,6 +93,7 @@ typedef struct SegmentContext {
>      char *time_str;        ///< segment duration specification string
>      int64_t time;          ///< segment duration
>      int use_strftime;      ///< flag to expand filename with strftime

> +    int increment_tc;      ///< flag for increment timecode if found

nit: flag to increment ...

>  
>      char *times_str;       ///< segment times specification string
>      int64_t *times;        ///< list of segment interval specification
> @@ -221,6 +223,30 @@ static int segment_start(AVFormatContext *s, int write_header)
>      SegmentContext *seg = s->priv_data;
>      AVFormatContext *oc = seg->avf;
>      int err = 0;
> +    AVTimecode tc;
> +    AVRational rate;
> +    

> +    if (seg->increment_tc){

style nit: if (...)_{

here and below

> +        AVDictionaryEntry * tcr = av_dict_get(s->metadata, "timecode", NULL, 0);
> +        if (tcr){
> +            if (s->nb_streams > 0){

> +                rate = s->streams[0]->avg_frame_rate;//Get fps from first stream

this looks a bit arbitrary, why the first stream?

> +                err = av_timecode_init_from_string(&tc, rate, tcr->value, s);
> +                if (err < 0)
> +                    return err;

> +                tc.start += (int)(seg->time / 1000000.) * av_q2d(rate);//second count * fps

You're losing precision here. Consider using the rescaling utilities
in libavutil/mathematics.h or something like (seg->time * rate.num) /
(rate.den * 1000000).

[...]
-- 
FFmpeg = Frightening & Faithful Mythic Programmable Elastic Gadget