[vlc-devel] [PATCH 1/4] mkv/demux: fix 17567: null-pointer dereference in EnsureDuration

Rémi Denis-Courmont remi at remlab.net
Wed Nov 2 13:50:12 CET 2016

Le 2016-11-02 12:10, Steve Lhomme a écrit :
> On Wed, Nov 2, 2016 at 11:00 AM, Rémi Denis-Courmont 
> <remi at remlab.net> wrote:
>> Le 2016-11-02 11:29, Steve Lhomme a écrit :
>>> To summarize the issue, is STREAM_CAN_FASTSEEK_FORWARD needed ?
>> I cannot comment on MKV spec. But I think you will not achieve 
>> anything with
>> STREAM_CAN_FASTSEEK_FORWARD. Specifically, I do not know any 
>> underlying
>> access or stream filter that would support or seeking fast in only 
>> one
>> direction.
> I think we discussed that in the past, but in the end we have no way
> how "fast" is the fast seeking anyway. On a network mounted drive the
> OS may report it can seek as much as you want but there's no 
> guarantee
> it will be fast.

We can disable file plug-in fast seeking based on the file system type. 
We already adjust the caching value.

But back to the point, fast seeking is not dependent on the direction 
of the seek. So I don´t see the point in STREAM_CAN_FASTSEEK_FORWARD. 
And if you meant small forward seek, well then all streams support that: 
just read the data into NULL.

Rémi Denis-Courmont

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