[FFmpeg-devel] [PATCH] MMS protocol support patch 1

Michael Niedermayer michaelni
Sun Sep 30 02:03:32 CEST 2007


On Tue, Sep 25, 2007 at 05:51:52PM +0200, Bj?rn Axelsson wrote:
> On Sat, 2007-09-22 at 02:43 +0200, Michael Niedermayer wrote:
> > Hi
> > 
> > On Wed, Sep 19, 2007 at 05:51:16PM +0200, Bj?rn Axelsson wrote:
> > > Hi,
> > > this is the first patch for MMS protocol support. Since the last RFC i
> > > have cleaned it up overall, split it up into several files and selected
> > > a minimal functional subset for your reviewing pleasure. I know it is
> > > still a lot of code to review, but it should at least be better than the
> > > last monster MMS patch.
> > > 
> > > This patch only includes mmsh (MMS over HTTP) support to keep it as
> > > small as possible. It also appears to be what most servers support. Some
> > > of the generic mms code make more or less obvious references to the mmst
> > > (MMS over TCP) protocol, which I hope is ok since that implementation
> > > will be added in a later patch.
> > > 
> > > When (if?) this is accepted I have some separate patches planned:
> > > - mmst support (implemented, just waiting for the smoke to clear)
> > > - mms protocol that chooses the best possible of the existing
> > > subprotocols (either mmst or mmsh)
> > 
> > > - clean API for controlling protocols (seek, play, pause).
> > 
> > its ok if you cleanup the API after adding MMS support but i will not accept
> > hacks in the code due to a missing clean API, that is if you can simply
> > remove/split out the parts which would need API changes then thats fine
> > otherwise the API cleanup will have to be done first
> Ok. Attached is a first draft for the API additions. It passes
> regression tests and performs well with an adjusted MMS patch.
> The goal is to expose a protocol-level API for functionality similar to
> read_play, read_pause and read_seek in AVInputFormat. The utility of
> protocol-level play/pause is obvious, and read_seek enables usage of
> server-side indices for seeking to specific time points.
> The highest level API is still av_play(), av_pause() and av_seek_frame()
> and most applications should require no changes.
> There are a couple of weak points I'd like some feedback on, though:
> - After a protocol-level seek most demuxers would need to be notified so
> that they can reset their current state. In the patch I chose the
> easiest solution: each demuxer need to implement support for
> protocol-level seeking as I have done in asf.c in the patch. An
> alternative would be to add a read_flush() or similar call to
> AVInputFormat and do the protocol-level seeking in av_seek_frame().
> - AVInputFormat:read_seek() takes a stream_index parameter which makes
> little sense for a protocol. Correctly supporting would require the
> URLProtocol to maintain an AVFormatContext parallel to that of the
> demuxer with the hope that stream indices are identical in both.
> Additionally, there's still no guarantee that the actual protocol
> supports time point seeking in specific streams. The attached patch
> keeps the stream_index parameter for the URLProtocol:url_read_seek, but
> allows it to be "-1" for "any stream". A cleaner solution would be to
> drop that parameter from the URLProtocol and ByteIOContext read_seek,
> but then their semantics would differ even more from
> AVInputformat:read_seek and it would be much harder to add support for
> stream_index in the future.
> (My MMS implementation does use a "shadow" AVFormatContext, but will
> still not be able to honor stream_index since it is unknown if it is
> possible with MMS to select a specific stream when seeking to a time
> point.)
> Without the stream_index parameter it would be possible to merge
> url_read_seek into url_seek with a special whence parameter, e.g.

i wish i could give you some feedback on these but iam not sure what is
best either ...


> Index: libavformat/avformat.h
> ===================================================================
> --- libavformat/avformat.h	(revision 10573)
> +++ libavformat/avformat.h	(arbetskopia)
> @@ -21,8 +21,8 @@
>  #ifndef AVFORMAT_H
>  #define AVFORMAT_H
> -#define LIBAVFORMAT_VERSION_INT ((51<<16)+(13<<8)+4)
> -#define LIBAVFORMAT_VERSION     51.13.4
> +#define LIBAVFORMAT_VERSION_INT ((52<<16)+(0<<8)+0)
> +#define LIBAVFORMAT_VERSION     52.0.0

ahh, great, theres no easy way to avoid that i guess?
these additions in ByteIOContext and its use in AVFormatContext :(
maybe we should think about if we at least can correct the code so
similar extensions in the future wont require a major version bump

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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