Hi,
august wrote
>
>> You pass the plugin registry because the encoder needs to load plugins.
>> The section however will be *not* the same section you pass to the
>> plugin registry in bg_plugin_registry_create(). See below.
>
>
>> Then you need to build the parameters, which describe this encoder
>> setup:
>>
>> bg_parameter_info_t * enc_parameters =
>> bg_plugin_registry_create_encoder_parameters(plugin_reg,
>> stream_mask,
>> plugin_mask);
>
> Is this just one set of parameters? What ends up in there? Is it an
> array of parameters for format/audio codec/video codec?
Look at the encoder configuration of the recorder, it's built from
the enc_parameters. It contains the menus for the encoding plugins
and several checkbuttons, where you can write audio into a separate
file etc.
>> Then you need a section, which contains the parameter values. The
>> parameter values are taken from what is saved in the config registry:
>>
>> bg_cfg_section_t * encoder_section =
>> bg_encoder_section_get_from_registry(plugin_reg,
>> enc_parameters,
>> stream_mask,
>> plugin_mask);
>
> Ok, so I see I use the enc_parameters to get a section. What is
> actually going on here?
It sets up the parameters for encoding. In particular it fills the
multi_names and multi_labels etc. from the actually installed plugins.
This whole thing was developed such, that the core *never* has to care,
which plugins are actually installed, so we build this stuff at runtime.
> Is the following correct?
> A registry is a collection of sections, right?
A config registry, yes.
>From include/registry_private.h:
struct bg_cfg_registry_s
{
bg_cfg_section_t * sections; /* Chained list of toplevel sections */
};
> And a section is a collection of parameters?
Yes, but it can also contain subsections.
> A config registry is a collection of configuration sections/parameters,
> right?
A config registry contains just the toplevel sections. If can't contain
parameters at the toplevel.
> A plugin registry is a collection of existing plugin sections with
> default parameters? Or, does it contain the paramater ranges too?
It's a collection of bg_plugin_info_t's
And for each plugin it knows where to find the config section.
The parameters are in the following members of bg_plugin_info_t:
/* Per instance parameters, existing for all plugins */
bg_parameter_info_t * parameters;
/* Per stream parameters, exist only for encoders */
bg_parameter_info_t * audio_parameters;
bg_parameter_info_t * video_parameters;
bg_parameter_info_t * subtitle_text_parameters;
bg_parameter_info_t * subtitle_overlay_parameters;
The bg_parameter_info_t contains both the range (val_min, val_max, for
numeric parameters) and a default value (val_default).
> Why do I create a plugin registry from a section in the config registry
> with :
>
> section = bg_cfg_registry_find_section(config_reg, "plugins");
> plugin_reg = bg_plugin_registry_create(section);
Because the plugin registry calls set_parameter() with the values taken
from the config section when a plugin is loaded.
This makes sure, that all plugins loaded with bg_plugin_load() have
the internal variables set such they at least don't crash.
>
>
>
>
>
> I then go on and do as you say:
>
> const int stream_mask = BG_STREAM_AUDIO | BG_STREAM_VIDEO;
> const int plugin_mask = BG_PLUGIN_FILE | BG_PLUGIN_BROADCAST ;
Correct
>
>
> enc_parameters = bg_plugin_registry_create_encoder_parameters(
> plugin_reg,
> stream_mask, plugin_mask);
>
Correct
>
> encoder_section = bg_encoder_section_get_from_registry(plugin_reg,
> enc_parameters,
> stream_mask,
> plugin_mask);
Correct
>
> encoder = bg_encoder_create( plugin_reg, encoder_section, NULL,
> stream_mask, plugin_mask);
Correct
>
> if ( bg_encoder_open( encoder, "testvideo", NULL, NULL)) {
>
> // What is the return value for bg_encoder_add_*_stream?
> // is it the stream index or 0 for no errors?
The stream index. You should remember them and pass them to
the encode() functions.
> astream = bg_encoder_add_audio_stream(encoder, NULL, &aformat, 0);
> vstream = bg_encoder_add_video_stream(encoder, &vformat, 1);
I think the last argument for bg_encoder_add_video_stream() should
also be zero. It's only needed if streams are written to separate files.
Then they get names like testvideo_audio01.mp3, testvideo_video01.avi.
> // at this point both astream and vstream = 0
> // Is that right?
Yes, stream indices are counted for audio and video separately.
>
> bg_encoder_start(encoder);
Would be wise to check if bg_encoder_start() returns 1.
0 means error.
> // I then get and check the in and out formats to see if they are ok
> bg_encoder_get_audio_format(encoder, astream, &aformat_out);
> bg_encoder_get_video_format(encoder, vstream, &vformat_out);
>
> // I check the formats with
> // gavl_audio_formats_equal (&aformat, &aformat_out)
> // gavl_video_formats_equal (&vformat, &vformat_out)
> // they are equal so I continue
If not, you can make gavl converters.
> // create audio and video frames
>
> aframe_out = gavl_audio_frame_create ( &aformat_out );
> vframe_out = gavl_video_frame_create_nopad ( &vformat_out );
> for (m=0; m < NUMBER_OF_FRAMES; m++) {
>
> // generate audio video content with some sine waave
>
> // then write the data
> bg_encoder_write_audio_frame(encoder, aframe_out, 0);
>
> // I can write the audio frame...but the I get a segfault
> // when I write the video frame
> bg_encoder_write_video_frame(encoder, vframe_out, 1);
>
> }
>
> }
>
Did you test that?
Burkhard
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