[FFmpeg-devel] ffmpeg_filter: switch sub2video.end_pts initialization value to 0

Submitted by Jan Ekström on Feb. 22, 2019, 7:56 p.m.

Details

Message ID 20190222195635.18530-1-jeebjp@gmail.com
State New
Headers show

Commit Message

Jan Ekström Feb. 22, 2019, 7:56 p.m.
This seems to fix use cases where the sub2video output is the only
input to a filter chain.

Additionally, this is the value to which the structure's values
would implicitly get initialized to. The ballooning buffering case
would not get hit by this as the value of end_pts after
(re-)initialization would be less than INT64_MAX, thus hitting the
sub2video AVFrame initialization logic via sub2video_update in
sub2video_heartbeat.
---
 fftools/ffmpeg_filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Jan Ekström Feb. 22, 2019, 8:22 p.m.
On Fri, Feb 22, 2019 at 9:56 PM Jan Ekström <jeebjp@gmail.com> wrote:
>
> This seems to fix use cases where the sub2video output is the only
> input to a filter chain.
>
> Additionally, this is the value to which the structure's values
> would implicitly get initialized to. The ballooning buffering case
> would not get hit by this as the value of end_pts after
> (re-)initialization would be less than INT64_MAX, thus hitting the
> sub2video AVFrame initialization logic via sub2video_update in
> sub2video_heartbeat.
> ---
>  fftools/ffmpeg_filter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
> index 72838de1e2..536f9c9c46 100644
> --- a/fftools/ffmpeg_filter.c
> +++ b/fftools/ffmpeg_filter.c
> @@ -739,7 +739,7 @@ static int sub2video_prepare(InputStream *ist, InputFilter *ifilter)
>      if (!ist->sub2video.frame)
>          return AVERROR(ENOMEM);
>      ist->sub2video.last_pts = INT64_MIN;
> -    ist->sub2video.end_pts  = INT64_MIN;
> +    ist->sub2video.end_pts  = 0;
>      return 0;
>  }
>
> --
> 2.20.1
>

An alternative for this would be to:
1. add a flag to sub2video structure that timestamp initialization is
required, and set it as required during (re-)initializations.
2. pass heartbeat pts to sub2video_update
3. finally, in sub2video_update
    } else {
        pts       = !ist->sub2video.timestamp_initialized ?
heartbeat_pts : ist->sub2video.end_pts;
        end_pts   = INT64_MAX;
        num_rects = 0;
    }
   and ist->sub2video.timestamp_initialized = 1; at the end.

This way the sub2video logic would start with the first heartbeat's
timestamp (often zero, but not always), as opposed to the initial
value of end_pts.

Jan

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diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index 72838de1e2..536f9c9c46 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -739,7 +739,7 @@  static int sub2video_prepare(InputStream *ist, InputFilter *ifilter)
     if (!ist->sub2video.frame)
         return AVERROR(ENOMEM);
     ist->sub2video.last_pts = INT64_MIN;
-    ist->sub2video.end_pts  = INT64_MIN;
+    ist->sub2video.end_pts  = 0;
     return 0;
 }