[FFmpeg-devel] [PATCH 2/2] RFC ffmpeg: exit demuxers earlier after signal received

[Andriy Gelman]

On Sat, 28. Nov 14:46, Andriy Gelman wrote:
> From: Andriy Gelman <andriy.gelman at gmail.com>
> 
> We currently use the same interrupt_callback function for both muxers
> and demuxers to break out of potential infinite loops.
> 
> The function decode_interrupt_cb() checks for how many SIGINT/SIGTERM
> interrupts have been received, and (usually) two interrupts are needed to
> break out of an infinite loop.
> 
> If this condition is seen on the muxer, however, we will fail to flush the
> avio buffers (see retry_transfer_wrapper()).
> An example of this issue is seen in Ticket #9009 (which would be fixed
> by this patch).
> 
> A more robust alternative maybe to break out of demuxers with one
> interrupt. The error should propagate through, close the muxers and
> allow them to flush properly.
> (If the infinite loop is present on the muxer then a second interrupt would
> cause it break out and have the same behavior as before.)
> 
> This patch adds this behavior. I've labelled it RFC because it
> potentially touches many demuxers.
> ---
>  fftools/ffmpeg.c     | 6 ++++++
>  fftools/ffmpeg.h     | 1 +
>  fftools/ffmpeg_opt.c | 2 +-
>  3 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> index 01f4ef15d8..bb27eec879 100644
> --- a/fftools/ffmpeg.c
> +++ b/fftools/ffmpeg.c
> @@ -510,7 +510,13 @@ static int decode_interrupt_cb(void *ctx)
>      return received_nb_signals > atomic_load(&transcode_init_done);
>  }
>  
> +static int decode_interrupt_one_sig_cb(void *ctx)
> +{
> +    return received_nb_signals > 0;
> +}
> +
>  const AVIOInterruptCB int_cb = { decode_interrupt_cb, NULL };
> +const AVIOInterruptCB int_one_sig_cb = { decode_interrupt_one_sig_cb, NULL };
>  
>  static void ffmpeg_cleanup(int ret)
>  {
> diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
> index 3b54dab7fc..c49af30009 100644
> --- a/fftools/ffmpeg.h
> +++ b/fftools/ffmpeg.h
> @@ -627,6 +627,7 @@ extern int vstats_version;
>  extern int auto_conversion_filters;
>  
>  extern const AVIOInterruptCB int_cb;
> +extern const AVIOInterruptCB int_one_sig_cb;
>  
>  extern const OptionDef options[];
>  extern const HWAccel hwaccels[];
> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c
> index 7ee034c9c9..2908f23010 100644
> --- a/fftools/ffmpeg_opt.c
> +++ b/fftools/ffmpeg_opt.c
> @@ -1156,7 +1156,7 @@ static int open_input_file(OptionsContext *o, const char *filename)
>      ic->flags |= AVFMT_FLAG_NONBLOCK;
>      if (o->bitexact)
>          ic->flags |= AVFMT_FLAG_BITEXACT;
> -    ic->interrupt_callback = int_cb;
> +    ic->interrupt_callback = int_one_sig_cb;
>  
>      if (!av_dict_get(o->g->format_opts, "scan_all_pmts", NULL, AV_DICT_MATCH_CASE)) {
>          av_dict_set(&o->g->format_opts, "scan_all_pmts", "1", AV_DICT_DONT_OVERWRITE);
> -- 
> 2.28.0
> 

ping

-- 
Andriy