[vlc-devel] [PATCH] access/avio: report FASTSEEK capability based on scheme and seekability

[Felix Paul Kühne]

Hello,

Please open a merge request. Contributions by patch through the mailing-list are no longer accepted.

Best regards,

Felix

> On 20. Apr 2026, at 00:15, Namit Chugh <nchugh1208 at gmail.com> wrote:
> 
> STREAM_CAN_FASTSEEK was hardcoded to false regardless of the
> underlying source. For local files opened via libavformat, random
> access is O(1) and fast seek should be advertised correctly — VLC
> uses this flag to decide whether to attempt seek-ahead buffering
> optimisations.
> 
> The fix ties STREAM_CAN_FASTSEEK to two conditions: libavformat
> reports the context as seekable, and the access scheme is "file".
> Network schemes like http or rtsp can seek but not cheaply, so they
> correctly continue to return false.
> 
> STREAM_CAN_SEEK is unchanged — it already reads sys->context->seekable
> directly and covers the general case.
> 
> --- a/modules/access/avio.c
> +++ b/modules/access/avio.c
> @@ -322,7 +322,8 @@ static int Control(stream_t *access, int query, va_list args)
>      case STREAM_CAN_FASTSEEK:
>          b = va_arg(args, bool *);
> -        *b = false;
> +        *b = sys->context->seekable &&
> +             !strcmp(access->psz_name, "file");
>          return VLC_SUCCESS;
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