[osflash] live streaming, FLV metadata, etc

[John Grden]

Hey Robert, can we have you re-post this question over on the Red5 mailing
list?

to join:
http://osflash.org/mailman/listinfo/red5_osflash.org

Thanks for your help!

John

On 5/8/07, Robert Prince <robert at theunixman.com> wrote:
>
> Hello all,
>
> First thanks to the developers for an awesome effort, and a very usable
> open source application.  :)
>
> What I'm doing is the following:
>
> 1) capture live video from webcam (format is MP4 in AVI) using mencoder
> to capture and also transcode on the fly to FLV
> 2) use flvtool2 to annotate captured file with FLV metadata for
> duration, keyframes, etc
> 3) resulting file progressive download/streamed using lighttpd (I am
> considering moving to red5)
>
> Now, on to the questions.  I've scanned the last few months archive of
> this list, and I haven't found answers (I think ;) ), so here we go.
>
> Is the FLV metadata (duration, keyframe info, etc) all in the header at
> the beginning of the file, or is it also spread out through the file?
> Looking at annotated FLV files with a hex editor leads me to think it's
> at the beginning, but I downloaded and read the FLV/SWF spec
>
> ** WARNING DEVELOPERS THAT NEED TO NOT KNOW THE SPEC, SKIP UNTIL YOU SEE
> /WARNING  **
> (that's for those who reverse engineer and thus cannot read the spec)
>
> and while the spec confuses me a bit, it leads me to believe that the
> metadata is spread throughout the file.
>
> ** /WARNING OKAY, IT'S SAFE TO READ BELOW **
>
> I've scanned the red5 code but I'm still confused (maybe I need to read
> it more thoroughly).  I've also looked at the flvtool2 code, but I'm not
> a Ruby guy, and it doesn't look sane.  Also there's a Python lib called
> "flashticle" that I'm looking at but so far I haven't answered my
> question.
>
> Next question, about live vs. progressive streaming.  I'm using the same
> process above to capture and transcode video, but then immediately
> streaming it out to a browser/player without doing the metadata
> annotation step.  I was hoping the player would be able to treat video
> it's already played as if it were annotated, i.e., I wanted the player
> to be able to move backwards in the stream with the scrubber, and then
> jump back to the front of the stream, catching the live video again.
> What happens instead is that
> the player plays the whole stream back from where it started, rather
> than being able to move to an arbitrary point in the past, and it can't
> get back to the start without reloading.
>
> Is this normal behavior when streaming live?  Is it a characteristic of
> the specific player I'm using?  (I'm using a commercial player with some
> custom modifications, done by the vendor).
>
> If this is simply how live streaming works, and the FLV metadata needs
> to be part of the file, I am considering developing a mechanism to add
> FLV metadata annotation to the transcoding step.  However, I know that
> duration can't be set - it's not known until the streaming stops!  But,
> can flash players be "tricked" by something like, say, setting duration
> to 0 or -1 or 99999?
>
>
> Thanks to all for taking the time to read this long-winded post!
>
>
> Cheers,
>
> Robert
>
> _______________________________________________
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> osflash at osflash.org
> http://osflash.org/mailman/listinfo/osflash_osflash.org
>



-- 
[  JPG  ]
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