libobs: Fix sending unclamped audio to output handler

[norihiro]

Description

The variable input.conversion.allow_clipping was left uninitialized. This could result in randomly sending unclamped audio to the output handlers that did not request the conversion.

To avoid the same initialized variables again when adding a new variable to the structure, I initialized audio at the declaration so that all other variables are initialized to zero.

Motivation and Context

The member variable allow_clipping was introduced by the commit dcee4fc in #8289.

In the function audio_output_connect, which allows the parameter conversion to be null to indicate no conversion is requested,
the variable allow_clipping was not initialized when the conversion was not requested.

I'm writing a plugin that calls audio_output_connect through obs_add_raw_audio_callback like this.
When following the code to see what is the default value of allow_clipping, I realized it was never initialized.

How Has This Been Tested?

Had a modification below to log allow_clipping just before it was used.

diff --git a/libobs/media-io/audio-io.c b/libobs/media-io/audio-io.c
index 18911ea58..06b922a13 100644
--- a/libobs/media-io/audio-io.c
+++ b/libobs/media-io/audio-io.c
@@ -117,6 +117,8 @@ static inline void do_audio_output(struct audio_output *audio, size_t mix_idx,
 	for (size_t i = mix->inputs.num; i > 0; i--) {
 		struct audio_input *input = mix->inputs.array + (i - 1);
 
+		blog(LOG_INFO, "%s: i=%zu: allow_clipping=%d", __func__, i, (int)input->conversion.allow_clipping);
+
 		float(*buf)[AUDIO_OUTPUT_FRAMES] =
 			input->conversion.allow_clipping ? mix->buffer_unclamped
 							 : mix->buffer;

Then, called obs_add_raw_audio_callback twice with conversion = NULL.

Checked the log and saw allow_clipping is uninitialized.

Without this commit, allow_clipping sometimes get non-zero value.

info: do_audio_output: i=1: allow_clipping=0
info: do_audio_output: i=2: allow_clipping=255

With this commit, I confirmed allow_clipping is always 0.

do_audio_output: i=1: allow_clipping=0
do_audio_output: i=2: allow_clipping=0

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[derrod]

An oversight on my part when I originally introduced this feature.

Hopefully we've not blown anybody's ears out by allowing audio on Twitch to clip 😅