PR: https://github.com/ytdl-org/youtube-dl/pull/29688
Closes: #617, https://github.com/ytdl-org/youtube-dl/issues/29665
* Livestreams are untested
* If using ffmpeg as downloader, v4.3+ is needed since `-http_seekable` option is necessary
* Instead of making a seperate key for each arg that needs to be passed to ffmpeg, I made `_ffmpeg_args`
* This deprecates `_seekable`, but the option is kept for compatibility
Authored by: nchilada, pukkandan
* Renamed `--external-downloader-args` to `--downloader-args`
* Added `native` as an option for the downloader
* Use similar syntax to `--downloader-args` etc. Eg: `--downloader dash:native --downloader aria2c`
* Deprecated `--hls-prefer-native` and `--hls-prefer-ffmpeg` since the same can now be done with `--downloader "m3u8:native"` and `m3u8:ffmpeg` respectively
* Split `frag_urls` protocol into `m3u8_frag_urls` and `dash_frag_urls`
* Standardize shortening of protocol names with `downloader.shorten_protocol_name`
* Create `FFmpegPostProcessor.real_run_ffmpeg` that can accept multiple input/output files along with switches for each
* Rewrite `cli_configuration_args` and related functions
* Create `YoutubeDL._ensure_dir_exists` - this was previously defined in multiple places
* Option `--concurrent-fragments` (`-N`) to set the number of threads
Related: #165
Known issues:
* When receiving Ctrl+C, the process will exit only after finishing the currently downloading fragments
* The download progress shows the speed of only one thread
Authored by shirt-dev
* Fix error when there is no `protocol` in `info_dict`
* Move HLS byte range detection to `Aria2cFD` so that the download will fall back to the native downloader instead of ffmpeg
* Fix bug with getting no fragments in DASH
* Convert `check_results` in `can_download` to a generator
* All modules and binary names are changed
* All documentation references changed
* yt-dlp no longer loads youtube-dlc config files
* All URLs changed to point to organization account
Co-authored-by: Pccode66
Co-authored-by: pukkandan
