[rtmpdump] Why does --swfVfy require an argument?

David Woodhouse dwmw2 at infradead.org
Tue May 11 18:18:01 CEST 2010

On Tue, 2010-05-11 at 08:43 -0700, Howard Chu wrote:
> David Woodhouse wrote:
> > On Tue, 2010-05-11 at 06:45 -0700, Howard Chu wrote:
> >> David Woodhouse wrote:
> >>> Utilities like get_iplayer will already pass a --swfUrl argument; why do
> >>> I need to provide it again?
> >>
> >> The manpage says why.
> >>
> >> The swfVfy option was intended to replace the swfUrl option.
> >
> > Unfortunately that's not massively practical. People who write tools
> > like get_iplayer are too scared to include explicit references to
> > rtmpdump and --swfVfy; they use flvstreamer instead and leave the task
> > of actually making things _work_ to the end-user.
> >
> > If we could just enable SWF Verification (or have it default to being
> > enabled) without having to re-provide the SWF URL, that would be a lot
> > easier.
> It's far too late to be questioning this now. The option has already been 
> deployed through several versions.
> Also, I was in close communication with the get_iplayer author when this 
> option was added, he didn't have any problem with it. You seem to be putting 
> words into other people's mouths.

Unfortunately the original author of get_iplayer author has now stopped
working on it -- precisely because of the SWF Verification issue.

When I asked the owner of the get_iplayer project on github, he said
"I can't support it directly in get_iplayer".

> There are good reasons not to leave SWF verification enabled all the time in 
> the code. It changes the handshake version, and it frequently costs time both 
> in making an HTTP connection to retrieve the SWF, and in computing the actual 
> hash and response.

Yeah, I did look briefly at that option and decide that it wasn't

> It was a good decision at the time. In retrospect it may not have been so 
> great. In the new API swfVfy is a boolean option, but I don't see how to 
> smoothly transition rtmpdump to the new API just yet.

One possibility is to add a command-line option which _is_ a boolean,
and just enables the swfVfy flag without affecting swfURL. That doesn't
break compatibility with the existing --swfVfy option. You could call it
something like --enableSwfVfy.


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