File Seek in the beginning of streaming

Hi,
I am trying to study the behavior of FileStream in the
beginning of
streaming in Helix.
I notice that Helix first tries to seek to end of the file,
read 4K
off the file and then re-seek the file to the beginning and
start
streaming from there.

My question is why it seeks to the end of the file in the
beginning?

Thank you.

_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

What kind of file is being streamed?

Most likely this is a type of file that doesn't
have the necessary header information at the beginning
of the file (i.e. - mp3). Therefore, the file format
plugin has to seek to the end of the file to get
some information before going back and starting
to deliver packets.

Eric

=============================================
Eric Hyche (ehychereal.com)
Technical Lead
RealNetworks, Inc.  

> -----Original Message-----
> From: filesystem-dev-bounceshelixcommunity.org 
> [mailto:filesystem-dev-bounceshelixcommunity.org] On
Behalf 
> Of ken carlino
> Sent: Wednesday, March 21, 2007 12:32 PM
> To: filesystem-devhelixcommunity.org
> Subject: [Filesystem-dev] File Seek in the beginning of
streaming
> 
> Hi,
> I am trying to study the behavior of FileStream in the
beginning of
> streaming in Helix.
> I notice that Helix first tries to seek to end of the
file, read 4K
> off the file and then re-seek the file to the beginning
and start
> streaming from there.
> 
> My question is why it seeks to the end of the file in
the beginning?
> 
> Thank you.
> 
> _______________________________________________
> Filesystem-dev mailing list
> Filesystem-devhelixcommunity.org
> http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> 


_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

On 3/21/07, Eric Hyche <ehychereal.com> wrote:
>
> What kind of file is being streamed?
>
> Most likely this is a type of file that doesn't
> have the necessary header information at the beginning
> of the file (i.e. - mp3). Therefore, the file format
> plugin has to seek to the end of the file to get
> some information before going back and starting
> to deliver packets.
>

Thanks. I am trying to stream 3gp.

After reading your response, I use a tool from FFmpeg which
moves moov atom
to the front.  But after I use this to convert the movie and
use Helix
to stream,
i still see Helix to seek to the end of the move before seek
back to
the top of the movie and start streaming.

Can you please help me understand why helix still needs to
seek to the
end of the move?

Thank you.


// Details of the qt-faststart:

 * This utility rearranges a Quicktime file such that the
moov atom
 * is in front of the data, thus facilitating network
streaming.
 *
 * Compile this program using:
 *  make qt-faststart
 * Invoke the program with:
 *  qt-faststart <infile.mov> <outfile.mov>
 *
 * Notes: Quicktime files can come in many configurations of
top-level
 * atoms. This utility stipulates that the very last atom in
the file needs
 * to be a moov atom. When given such a file, this utility
will rearrange
 * the top-level atoms by shifting the moov atom from the
back of the file
 * to the front, and patch the chunk offsets along the way.
This utility
 * presently only operates on uncompressed moov atoms.



> Eric
>
> =============================================
> Eric Hyche (ehychereal.com)
> Technical Lead
> RealNetworks, Inc.
>
> > -----Original Message-----
> > From: filesystem-dev-bounceshelixcommunity.org
> > [mailto:filesystem-dev-bounceshelixcommunity.org] On Behalf
> > Of ken carlino
> > Sent: Wednesday, March 21, 2007 12:32 PM
> > To: filesystem-devhelixcommunity.org
> > Subject: [Filesystem-dev] File Seek in the
beginning of streaming
> >
> > Hi,
> > I am trying to study the behavior of FileStream in
the beginning of
> > streaming in Helix.
> > I notice that Helix first tries to seek to end of
the file, read 4K
> > off the file and then re-seek the file to the
beginning and start
> > streaming from there.
> >
> > My question is why it seeks to the end of the file
in the beginning?
> >
> > Thank you.
> >
> > _______________________________________________
> > Filesystem-dev mailing list
> > Filesystem-devhelixcommunity.org
> > http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> >
>
>

_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

Not sure off the top of my head. I would step through
the file format plugin in a debugger to be sure.
The .3gp file format is located in datatype/mp4/fileformat.

Eric

=============================================
Eric Hyche (ehychereal.com)
Technical Lead
RealNetworks, Inc.  

> -----Original Message-----
> From: ken carlino [mailto:ken.carlinogmail.com] 
> Sent: Friday, March 23, 2007 10:05 PM
> To: ehychereal.com
> Cc: filesystem-devhelixcommunity.org
> Subject: Re: [Filesystem-dev] File Seek in the
beginning of streaming
> 
> On 3/21/07, Eric Hyche <ehychereal.com> wrote:
> >
> > What kind of file is being streamed?
> >
> > Most likely this is a type of file that doesn't
> > have the necessary header information at the
beginning
> > of the file (i.e. - mp3). Therefore, the file
format
> > plugin has to seek to the end of the file to get
> > some information before going back and starting
> > to deliver packets.
> >
> 
> Thanks. I am trying to stream 3gp.
> 
> After reading your response, I use a tool from FFmpeg
which 
> moves moov atom
> to the front.  But after I use this to convert the
movie and use Helix
> to stream,
> i still see Helix to seek to the end of the move before
seek back to
> the top of the movie and start streaming.
> 
> Can you please help me understand why helix still needs
to seek to the
> end of the move?
> 
> Thank you.
> 
> 
> // Details of the qt-faststart:
> 
>  * This utility rearranges a Quicktime file such that
the moov atom
>  * is in front of the data, thus facilitating network
streaming.
>  *
>  * Compile this program using:
>  *  make qt-faststart
>  * Invoke the program with:
>  *  qt-faststart <infile.mov>
<outfile.mov>
>  *
>  * Notes: Quicktime files can come in many
configurations of top-level
>  * atoms. This utility stipulates that the very last
atom in 
> the file needs
>  * to be a moov atom. When given such a file, this
utility 
> will rearrange
>  * the top-level atoms by shifting the moov atom from
the 
> back of the file
>  * to the front, and patch the chunk offsets along the
way. 
> This utility
>  * presently only operates on uncompressed moov atoms.
> 
> 
> 
> > Eric
> >
> > =============================================
> > Eric Hyche (ehychereal.com)
> > Technical Lead
> > RealNetworks, Inc.
> >
> > > -----Original Message-----
> > > From: filesystem-dev-bounceshelixcommunity.org
> > > [mailto:filesystem-dev-bounceshelixcommunity.org] On Behalf
> > > Of ken carlino
> > > Sent: Wednesday, March 21, 2007 12:32 PM
> > > To: filesystem-devhelixcommunity.org
> > > Subject: [Filesystem-dev] File Seek in the
beginning of streaming
> > >
> > > Hi,
> > > I am trying to study the behavior of
FileStream in the 
> beginning of
> > > streaming in Helix.
> > > I notice that Helix first tries to seek to
end of the 
> file, read 4K
> > > off the file and then re-seek the file to the
beginning and start
> > > streaming from there.
> > >
> > > My question is why it seeks to the end of the
file in the 
> beginning?
> > >
> > > Thank you.
> > >
> > >
_______________________________________________
> > > Filesystem-dev mailing list
> > > Filesystem-devhelixcommunity.org
> > > http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> > >
> >
> >
> 


_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

Thanks. Can you please tell me how can i just debug the file
format plugin
after I start Helix server?

On 4/2/07, Eric Hyche <ehychereal.com> wrote:
>
> Not sure off the top of my head. I would step through
> the file format plugin in a debugger to be sure.
> The .3gp file format is located in
datatype/mp4/fileformat.
>
> Eric
>
> =============================================
> Eric Hyche (ehychereal.com)
> Technical Lead
> RealNetworks, Inc.
>
> > -----Original Message-----
> > From: ken carlino [mailto:ken.carlinogmail.com]
> > Sent: Friday, March 23, 2007 10:05 PM
> > To: ehychereal.com
> > Cc: filesystem-devhelixcommunity.org
> > Subject: Re: [Filesystem-dev] File Seek in the
beginning of streaming
> >
> > On 3/21/07, Eric Hyche <ehychereal.com> wrote:
> > >
> > > What kind of file is being streamed?
> > >
> > > Most likely this is a type of file that
doesn't
> > > have the necessary header information at the
beginning
> > > of the file (i.e. - mp3). Therefore, the file
format
> > > plugin has to seek to the end of the file to
get
> > > some information before going back and
starting
> > > to deliver packets.
> > >
> >
> > Thanks. I am trying to stream 3gp.
> >
> > After reading your response, I use a tool from
FFmpeg which
> > moves moov atom
> > to the front.  But after I use this to convert the
movie and use Helix
> > to stream,
> > i still see Helix to seek to the end of the move
before seek back to
> > the top of the movie and start streaming.
> >
> > Can you please help me understand why helix still
needs to seek to the
> > end of the move?
> >
> > Thank you.
> >
> >
> > // Details of the qt-faststart:
> >
> >  * This utility rearranges a Quicktime file such
that the moov atom
> >  * is in front of the data, thus facilitating
network streaming.
> >  *
> >  * Compile this program using:
> >  *  make qt-faststart
> >  * Invoke the program with:
> >  *  qt-faststart <infile.mov>
<outfile.mov>
> >  *
> >  * Notes: Quicktime files can come in many
configurations of top-level
> >  * atoms. This utility stipulates that the very
last atom in
> > the file needs
> >  * to be a moov atom. When given such a file, this
utility
> > will rearrange
> >  * the top-level atoms by shifting the moov atom
from the
> > back of the file
> >  * to the front, and patch the chunk offsets along
the way.
> > This utility
> >  * presently only operates on uncompressed moov
atoms.
> >
> >
> >
> > > Eric
> > >
> > >
=============================================
> > > Eric Hyche (ehychereal.com)
> > > Technical Lead
> > > RealNetworks, Inc.
> > >
> > > > -----Original Message-----
> > > > From: filesystem-dev-bounceshelixcommunity.org
> > > > [mailto:filesystem-dev-bounceshelixcommunity.org] On Behalf
> > > > Of ken carlino
> > > > Sent: Wednesday, March 21, 2007 12:32
PM
> > > > To: filesystem-devhelixcommunity.org
> > > > Subject: [Filesystem-dev] File Seek in
the beginning of streaming
> > > >
> > > > Hi,
> > > > I am trying to study the behavior of
FileStream in the
> > beginning of
> > > > streaming in Helix.
> > > > I notice that Helix first tries to seek
to end of the
> > file, read 4K
> > > > off the file and then re-seek the file
to the beginning and start
> > > > streaming from there.
> > > >
> > > > My question is why it seeks to the end
of the file in the
> > beginning?
> > > >
> > > > Thank you.
> > > >
> > > >
_______________________________________________
> > > > Filesystem-dev mailing list
> > > > Filesystem-devhelixcommunity.org
> > > > http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> > > >
> > >
> > >
> >
>
>

_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

The best place to start is to set a breakpoint at the
beginning of the file format's
IHXFileFormatObject::InitFileFormat(),
IHXFileFormatObject::GetFileHeader(), and
IHXFileFormatObject::GetStreamHeader()
methods. Then start the server and hit the server from
a client with a media type which will use the file format
you are interested in.

Eric

=============================================
Eric Hyche (ehychereal.com)
Technical Lead
RealNetworks, Inc.  

> -----Original Message-----
> From: ken carlino [mailto:ken.carlinogmail.com] 
> Sent: Tuesday, April 03, 2007 12:22 AM
> To: ehychereal.com
> Cc: filesystem-devhelixcommunity.org
> Subject: Re: [Filesystem-dev] File Seek in the
beginning of streaming
> 
> Thanks. Can you please tell me how can i just debug the
file 
> format plugin
> after I start Helix server?
> 
> On 4/2/07, Eric Hyche <ehychereal.com> wrote:
> >
> > Not sure off the top of my head. I would step
through
> > the file format plugin in a debugger to be sure.
> > The .3gp file format is located in
datatype/mp4/fileformat.
> >
> > Eric
> >
> > =============================================
> > Eric Hyche (ehychereal.com)
> > Technical Lead
> > RealNetworks, Inc.
> >
> > > -----Original Message-----
> > > From: ken carlino [mailto:ken.carlinogmail.com]
> > > Sent: Friday, March 23, 2007 10:05 PM
> > > To: ehychereal.com
> > > Cc: filesystem-devhelixcommunity.org
> > > Subject: Re: [Filesystem-dev] File Seek in
the beginning 
> of streaming
> > >
> > > On 3/21/07, Eric Hyche <ehychereal.com> wrote:
> > > >
> > > > What kind of file is being streamed?
> > > >
> > > > Most likely this is a type of file that
doesn't
> > > > have the necessary header information at
the beginning
> > > > of the file (i.e. - mp3). Therefore, the
file format
> > > > plugin has to seek to the end of the
file to get
> > > > some information before going back and
starting
> > > > to deliver packets.
> > > >
> > >
> > > Thanks. I am trying to stream 3gp.
> > >
> > > After reading your response, I use a tool
from FFmpeg which
> > > moves moov atom
> > > to the front.  But after I use this to
convert the movie 
> and use Helix
> > > to stream,
> > > i still see Helix to seek to the end of the
move before 
> seek back to
> > > the top of the movie and start streaming.
> > >
> > > Can you please help me understand why helix
still needs 
> to seek to the
> > > end of the move?
> > >
> > > Thank you.
> > >
> > >
> > > // Details of the qt-faststart:
> > >
> > >  * This utility rearranges a Quicktime file
such that the 
> moov atom
> > >  * is in front of the data, thus facilitating
network streaming.
> > >  *
> > >  * Compile this program using:
> > >  *  make qt-faststart
> > >  * Invoke the program with:
> > >  *  qt-faststart <infile.mov>
<outfile.mov>
> > >  *
> > >  * Notes: Quicktime files can come in many
configurations 
> of top-level
> > >  * atoms. This utility stipulates that the
very last atom in
> > > the file needs
> > >  * to be a moov atom. When given such a file,
this utility
> > > will rearrange
> > >  * the top-level atoms by shifting the moov
atom from the
> > > back of the file
> > >  * to the front, and patch the chunk offsets
along the way.
> > > This utility
> > >  * presently only operates on uncompressed
moov atoms.
> > >
> > >
> > >
> > > > Eric
> > > >
> > > >
=============================================
> > > > Eric Hyche (ehychereal.com)
> > > > Technical Lead
> > > > RealNetworks, Inc.
> > > >
> > > > > -----Original Message-----
> > > > > From: filesystem-dev-bounceshelixcommunity.org
> > > > > [mailto:filesystem-dev-bounceshelixcommunity.org] On Behalf
> > > > > Of ken carlino
> > > > > Sent: Wednesday, March 21, 2007
12:32 PM
> > > > > To: filesystem-devhelixcommunity.org
> > > > > Subject: [Filesystem-dev] File Seek
in the beginning 
> of streaming
> > > > >
> > > > > Hi,
> > > > > I am trying to study the behavior
of FileStream in the
> > > beginning of
> > > > > streaming in Helix.
> > > > > I notice that Helix first tries to
seek to end of the
> > > file, read 4K
> > > > > off the file and then re-seek the
file to the 
> beginning and start
> > > > > streaming from there.
> > > > >
> > > > > My question is why it seeks to the
end of the file in the
> > > beginning?
> > > > >
> > > > > Thank you.
> > > > >
> > > > >
_______________________________________________
> > > > > Filesystem-dev mailing list
> > > > > Filesystem-devhelixcommunity.org
> > > > > 
> http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> > > > >
> > > >
> > > >
> > >
> >
> >
> 


_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev

Eric,

Thanks for your help.
I find out that in the function
CQTFileFormat::GetFileHeader(), it
calls 'Atomize()'.
This is where Helix seek to the end of the file before it
start
streaming a mp4 file.

But I still can't figure out why Atomize() does it (seek to
the end of
the file).

On 4/4/07, Eric Hyche <ehychereal.com> wrote:
>
> The best place to start is to set a breakpoint at the
> beginning of the file format's
IHXFileFormatObject::InitFileFormat(),
> IHXFileFormatObject::GetFileHeader(), and
> IHXFileFormatObject::GetStreamHeader()
> methods. Then start the server and hit the server from
> a client with a media type which will use the file
format
> you are interested in.
>
> Eric
>
> =============================================
> Eric Hyche (ehychereal.com)
> Technical Lead
> RealNetworks, Inc.
>
> > -----Original Message-----
> > From: ken carlino [mailto:ken.carlinogmail.com]
> > Sent: Tuesday, April 03, 2007 12:22 AM
> > To: ehychereal.com
> > Cc: filesystem-devhelixcommunity.org
> > Subject: Re: [Filesystem-dev] File Seek in the
beginning of streaming
> >
> > Thanks. Can you please tell me how can i just
debug the file
> > format plugin
> > after I start Helix server?
> >
> > On 4/2/07, Eric Hyche <ehychereal.com> wrote:
> > >
> > > Not sure off the top of my head. I would step
through
> > > the file format plugin in a debugger to be
sure.
> > > The .3gp file format is located in
datatype/mp4/fileformat.
> > >
> > > Eric
> > >
> > >
=============================================
> > > Eric Hyche (ehychereal.com)
> > > Technical Lead
> > > RealNetworks, Inc.
> > >
> > > > -----Original Message-----
> > > > From: ken carlino
[mailto:ken.carlinogmail.com]
> > > > Sent: Friday, March 23, 2007 10:05 PM
> > > > To: ehychereal.com
> > > > Cc: filesystem-devhelixcommunity.org
> > > > Subject: Re: [Filesystem-dev] File Seek
in the beginning
> > of streaming
> > > >
> > > > On 3/21/07, Eric Hyche <ehychereal.com> wrote:
> > > > >
> > > > > What kind of file is being
streamed?
> > > > >
> > > > > Most likely this is a type of file
that doesn't
> > > > > have the necessary header
information at the beginning
> > > > > of the file (i.e. - mp3).
Therefore, the file format
> > > > > plugin has to seek to the end of
the file to get
> > > > > some information before going back
and starting
> > > > > to deliver packets.
> > > > >
> > > >
> > > > Thanks. I am trying to stream 3gp.
> > > >
> > > > After reading your response, I use a
tool from FFmpeg which
> > > > moves moov atom
> > > > to the front.  But after I use this to
convert the movie
> > and use Helix
> > > > to stream,
> > > > i still see Helix to seek to the end of
the move before
> > seek back to
> > > > the top of the movie and start
streaming.
> > > >
> > > > Can you please help me understand why
helix still needs
> > to seek to the
> > > > end of the move?
> > > >
> > > > Thank you.
> > > >
> > > >
> > > > // Details of the qt-faststart:
> > > >
> > > >  * This utility rearranges a Quicktime
file such that the
> > moov atom
> > > >  * is in front of the data, thus
facilitating network streaming.
> > > >  *
> > > >  * Compile this program using:
> > > >  *  make qt-faststart
> > > >  * Invoke the program with:
> > > >  *  qt-faststart <infile.mov>
<outfile.mov>
> > > >  *
> > > >  * Notes: Quicktime files can come in
many configurations
> > of top-level
> > > >  * atoms. This utility stipulates that
the very last atom in
> > > > the file needs
> > > >  * to be a moov atom. When given such a
file, this utility
> > > > will rearrange
> > > >  * the top-level atoms by shifting the
moov atom from the
> > > > back of the file
> > > >  * to the front, and patch the chunk
offsets along the way.
> > > > This utility
> > > >  * presently only operates on
uncompressed moov atoms.
> > > >
> > > >
> > > >
> > > > > Eric
> > > > >
> > > > >
=============================================
> > > > > Eric Hyche (ehychereal.com)
> > > > > Technical Lead
> > > > > RealNetworks, Inc.
> > > > >
> > > > > > -----Original Message-----
> > > > > > From:
filesystem-dev-bounceshelixcommunity.org
> > > > > >
[mailto:filesystem-dev-bounceshelixcommunity.org] On
Behalf
> > > > > > Of ken carlino
> > > > > > Sent: Wednesday, March 21,
2007 12:32 PM
> > > > > > To: filesystem-devhelixcommunity.org
> > > > > > Subject: [Filesystem-dev] File
Seek in the beginning
> > of streaming
> > > > > >
> > > > > > Hi,
> > > > > > I am trying to study the
behavior of FileStream in the
> > > > beginning of
> > > > > > streaming in Helix.
> > > > > > I notice that Helix first
tries to seek to end of the
> > > > file, read 4K
> > > > > > off the file and then re-seek
the file to the
> > beginning and start
> > > > > > streaming from there.
> > > > > >
> > > > > > My question is why it seeks to
the end of the file in the
> > > > beginning?
> > > > > >
> > > > > > Thank you.
> > > > > >
> > > > > >
_______________________________________________
> > > > > > Filesystem-dev mailing list
> > > > > > Filesystem-devhelixcommunity.org
> > > > > >
> > http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev
> > > > > >
> > > > >
> > > > >
> > > >
> > >
> > >
> >
>
>

_______________________________________________
Filesystem-dev mailing list
Filesystem-devhelixcommunity.org
http://lists.helixcommunity.org/mailman/listinfo/
filesystem-dev