Repository: yt-dlp/yt-dlp
File: yt_dlp/extractor/vk.py (Python)

Code before:
                mask_url[index] = c
            mask_url = ''.join(mask_url)
        return mask_url

    def _real_extract(self, url):
        post_id = self._match_id(url)

        webpage = self._download_payload('wkview', post_id, {
            'act': 'show',
            'w': 'wall' + post_id,
        })[1]

        description = clean_html(get_element_by_class('wall_post_text', webpage))
        uploader = clean_html(get_element_by_class('author', webpage))

        entries = []

        for audio in re.findall(r'data-audio="([^"]+)', webpage):
            audio = self._parse_json(unescapeHTML(audio), post_id)
            if not audio['url']:
                continue
            title = unescapeHTML(audio['title'])
            artist = unescapeHTML(audio['artist'])
            entries.append({
                'id': '%s_%s' % (audio['owner_id'], audio['id']),
                'url': audio['url'],
                'title': '%s - %s' % (artist, title) if artist else title,
                'thumbnails': [{'url': c_url} for c_url in audio['coverUrl'].split(',')] if audio['coverUrl'] else None,
                'duration': int_or_none(audio['duration']),
                'uploader': uploader,
                'artist': artist,
                'track': title,
                'ext': 'mov',
                'protocol': 'm3u8_native',
            })

        for video in re.finditer(
                r'<a[^>]+href=(["\'])(?P<url>/video(?:-?[\d_]+).*?)\1', webpage):
            entries.append(self.url_result(
                compat_urlparse.urljoin(url, video.group('url')), VKIE.ie_key()))

        title = 'Wall post %s' % post_id

        return self.playlist_result(
            orderedSet(entries), post_id,
            '%s - %s' % (uploader, title) if uploader else title,
            description)


Review comment (refactor):
I think I found the issue. Try removing `url`, `ext`, `protocol` and add `'formats': self._extract_m3u8_formats(...)` instead

Code after:
                index = indexes[url_len - 1 - n]
                mask_url[n] = mask_url[index]
                mask_url[index] = c
            mask_url = ''.join(mask_url)
        return mask_url

    def _real_extract(self, url):
        post_id = self._match_id(url)

        webpage = self._download_payload('wkview', post_id, {
            'act': 'show',
            'w': 'wall' + post_id,
        })[1]

        uploader = clean_html(get_element_by_class('PostHeaderTitle__authorName', webpage))

        entries = []

        for audio in re.findall(r'data-audio="([^"]+)', webpage):
            audio = self._parse_json(unescapeHTML(audio), post_id)
            if not audio['url']:
                continue
            title = unescapeHTML(audio.get('title'))
            artist = unescapeHTML(audio.get('artist'))
            entries.append({
                'id': f'{audio["owner_id"]}_{audio["id"]}',
                'title': join_nonempty(artist, title, delim=' - '),
                'thumbnails': try_call(lambda: [{'url': u} for u in audio['coverUrl'].split(',')]),
                'duration': int_or_none(audio.get('duration')),
                'uploader': uploader,
                'artist': artist,
                'track': title,
                'formats': [{
                    'url': audio['url'],
                    'ext': 'm4a',
                    'vcodec': 'none',
                    'acodec': 'mp3',
                    'container': 'm4a_dash',
                }],
            })

        entries.extend(self.url_result(urljoin(url, entry), VKIE) for entry in set(re.findall(
            r'<a[^>]+href=(?:["\'])(/video(?:-?[\d_]+)[^"\']*)',
            get_element_html_by_id('wl_post_body', webpage))))

        return self.playlist_result(
            entries, post_id, join_nonempty(uploader, f'Wall post {post_id}', delim=' - '),
            clean_html(get_element_by_class('wall_post_text', webpage)))