[pulseaudio-discuss] [PATCH 0/2] module-tunnel-source broken - Something went wrong at protocol version 22 :-(

[David Henningsson]

I'm trying to set up a module-tunnel-source, but it fails with a 
protocol error.

Here's the analysis.

According to spec:

<---
## v22, implemented by >= 1.0

New fields PA_COMMAND_CREATE_RECORD_STREAM:

     uint8_t n_formats
     format_info format1
     ...
     format_info formatn
--->


1) According to code in module-tunnel.c, the code for sending n_formats 
is missing.

2) More interesting is that according to code in protocol-native.c, not 
only does PA_COMMAND_CREATE_RECORD_STREAM assume the above to come in, 
but also these fields:

<---
         if (pa_tagstruct_get_cvolume(t, &volume) < 0 ||
             pa_tagstruct_get_boolean(t, &muted) < 0 ||
             pa_tagstruct_get_boolean(t, &volume_set) < 0 ||
             pa_tagstruct_get_boolean(t, &muted_set) < 0 ||
             pa_tagstruct_get_boolean(t, &relative_volume) < 0 ||
             pa_tagstruct_get_boolean(t, &passthrough) < 0) {
--->

...which is consistent with the code in src/pulse/stream.c. These are 
not documented in the PROTOCOL file.

3) Actually, they remotely correspond to something in the documentation 
for protocol v22 as well:

<---
Five new fields in reply from PA_COMMAND_GET_SOURCE_OUTPUT_INFO (and 
thus PA_COMMAND_GET_SOURCE_OUTPUT_INFO_LIST)

     format_info format
     volume
     bool mute
     bool has_volume
     bool volume_writable
--->

In the code, the format_info comes last instead of first. :-/

This is a problem both in PulseAudio 1.x and in git master. (And thus in 
Ubuntu 11.10 and Ubuntu 12.04.)

After some thoughts, I think the wisest course of action is to fixup 
module-tunnel to send more fields, and fixup the documentation to match 
the code. I'll send some patches for this. Next question is if we should 
also consider backwards compatibility with 1.x's broken implementation 
of module-tunnel-source...?

-- 
David Henningsson, Canonical Ltd.
http://launchpad.net/~diwic