[FFmpeg-user] Setting -output_ts_offset always adds 2 frames

[Julien De Luca]

After several tries, I noticed that doing :

ffmpeg -i clip.ts -c copy -y -copyts -mpegts_copyts 1 -ss -14
clip-correct-pts.ts

shifts the pts without modifyijng the video. So I did 2 passes after
retrieving the pts of the first frame to calculate the offset.

On Fri, Feb 8, 2019 at 8:14 AM Gyan <ffmpeg at gyani.pro> wrote:

>
>
> On 07-02-2019 03:47 AM, Julien De Luca wrote:
> > Hello all,
> >
> > I'm trying to set the initial pkt_pts_time using output_ts_offset. On
> > streams encoded using ffmpeg, it always sets the offset + 0.08s, which
> is 2
> > frames. Here is the command I use :
> >
> > ```
> > ffmpeg -i input.ts -acodec aac -vcodec libx264 -f mpegts -preset veryfast
> > -filter:v scale=640:-1 -framerate 25 -profile:v main -b:v 1200000 -level
> > 3.1 -b:a 96000 -g 75 -bf 3 -output_ts_offset 10 -muxdelay 0 -muxpreload 0
> > output.ts
> > ```
> >
> > And the output from ffprobe for the first video frame :
> > ```
> > {
> >    "media_type": "video",
> >    "stream_index": 0,
> >    "key_frame": 1,
> >    "pkt_pts": 907200,
> >    "pkt_pts_time": "10.080000",
> >    "pkt_dts": 907200,
> >    "pkt_dts_time": "10.080000",
> >    "best_effort_timestamp": 907200,
> >    "best_effort_timestamp_time": "10.080000",
> >    "pkt_duration": 3600,
> >    "pkt_duration_time": "0.040000",
> >    "pkt_pos": "1128",
> >    "pkt_size": "4872",
> >    "width": 640,
> >    "height": 360,
> >    "pix_fmt": "yuv420p",
> >    "sample_aspect_ratio": "1:1",
> >    "pict_type": "I",
> >    "coded_picture_number": 0,
> >    "display_picture_number": 0,
> >    "interlaced_frame": 0,
> >    "top_field_first": 0,
> >    "repeat_pict": 0,
> >    "chroma_location": "left"
> > }
> > ```
> >
> > The input is a ts file from a segmented stream created using hls options
> of
> > ffmpeg.
> >
> > On another input created using AWS Mediaconvert, pkt_pts_time is set
> > correctly, at exactly 10.
> >
> > Is there any known reason this may happen ?
> >
>
> What's the output with
>
> ffmpeg -i input.ts -an -vcodec libx264 -f mpegts -preset veryfast
> -filter:v scale=640:-1 -profile:v main -b:v 1200000 -level
> 3.1 -g 75 -bf 3 -output_ts_offset 10 -muxdelay 0 -muxpreload 0
> output.ts
>
> Gyan
>
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