I’m assuming you are using WordPress’ Embeds
feature. Generally speaking wp_embed_defaults() gives you the information you need. A look at the source discloses the possibilities you have:
2017 /**
2018 * Create default array of embed parameters.
2019 *
2020 * The width defaults to the content width as specified by the theme. If the
2021 * theme does not specify a content width, then 500px is used.
2022 *
2023 * The default height is 1.5 times the width, or 1000px, whichever is smaller.
2024 *
2025 * The 'embed_defaults' filter can be used to adjust either of these values.
2026 *
2027 * @since 2.9.0
2028 *
2029 * @return array Default embed parameters.
2030 */
2031 function wp_embed_defaults() {
2032 if ( ! empty( $GLOBALS['content_width'] ) )
2033 $width = (int) $GLOBALS['content_width'];
2034
2035 if ( empty( $width ) )
2036 $width = 500;
2037
2038 $height = min( ceil( $width * 1.5 ), 1000 );
2039
2040 /**
2041 * Filter the default array of embed dimensions.
2042 *
2043 * @since 2.9.0
2044 *
2045 * @param int $width Width of the embed in pixels.
2046 * @param int $height Height of the embed in pixels.
2047 */
2048 return apply_filters( 'embed_defaults', compact( 'width', 'height' ) );
2049 }
As you can see the global variable $content_width – $GLOBALS['content_width'] – is the first approach to determine the default width, if it isn’t empty it will be used. The theme feature Content Width can be used by adding the following to your functions.php:
if ( ! isset( $content_width ) ) {
$content_width = 1200;
}
Which sets up the width you need. If you don’t do that the width defaults to 500px, as you can see above. The height defaults either to 1.5 times the width or – if that is less – to 1000px.
The specified width is a maximum, so your embed won’t be wider then that, but will scale down in size. You can possibly support this behavior via CSS, with the following parameters:
max-width: 100%;
height: auto;
Which is generally a recommendation, but not necessarily needed.
The above should normally be enough to scale your embedded contents to the size of the container they are in.
However the look into the source shows another way of modifying the width (and height) value. Which would be by hooking into the embed_defaults filter. More general information about this functionality can be found via the WordPress codex page Plugin API, which is a good start to learn more about the topic. A specific example on how to apply this possibility to the embed_defaults filter looks like this:
add_filter( 'embed_defaults', 'wpse150029_change_embed_defaults' );
function wpse150029_change_embed_defaults() {
return array(
'width' => 1200,
'height' => 800
);
}
The code would be part of your functions.php or a plugin. Theoretically you can use conditional tags to differentiate the values, but it is unlikely needed.
This should cover the possibilities of setting up the width of your embedded content. The rest depends on your templates and the CSS of the theme you are using.
As your goal is to show the_excerpt() and the video on your home, front- or overview page you have to create your own function to extract the video URL from the post content and use wp_oembed_get() to fetch the embed HTML. For example like this:
function wpse150029_fetch_youtube_return_embed_html( $content ) {
// Regex example+explanation can be found here: http://regex101.com/r/vZ6bX6/3
// note: the first youtube link will be extracted
$pattern = '/(?<=(?:\[embed\])|(?:\[embed\]\s)|(?:))';
$pattern .= '(https?:\/\/)';
$pattern .= '(:?www\.)?';
$pattern .= '(:?youtube\.com\/watch|youtu\.be\/)';
$pattern .= '([\w\?\=\&(amp;)]+)';
$pattern .= '(?=(?:\[\/embed\])|(?:\s\[\/embed\])|(?:))';
$pattern .= '/ims';
preg_match( $pattern, $content, $matches );
$url = $matches[0];
$embed_code = wp_oembed_get( $url );
return $embed_code;
}
The above code goes into your functions.php. Exemplary usage in your template like shown below:
$video_loop = new WP_Query( $args );
if ( $video_loop->have_post() ) :
while ( $video_loop->have_posts() ) : $video_loop->the_post();
the_title();
the_excerpt();
echo wpse150029_fetch_youtube_return_embed_html( $post->post_content );
endwhile;
wp_reset_postdata();
else :
endif;
For a detailed description on that take a look at the WP_Query documentation.
If you are actually want to have thumbnails for your embedded videos, you should take a look at those Q&A’s on here: