从 1080p 分辨率开始，YouTube 就有了独立的音频和视频轨道。在下面的例子中，youtube-dl 认为 1280x720 流 ( 22) 是最佳的，因为更高分辨率的视频缺少音轨。
format code extension resolution note
249 webm audio only DASH audio 51k , opus @ 50k (48000Hz), 709.40KiB
250 webm audio only DASH audio 71k , opus @ 70k (48000Hz), 956.67KiB
171 webm audio only DASH audio 112k , vorbis@128k (44100Hz), 1.49MiB
140 m4a audio only DASH audio 127k , m4a_dash container, mp4a.40.2@128k (44100Hz), 1.74MiB
251 webm audio only DASH audio 140k , opus @160k (48000Hz), 1.80MiB
278 webm 256x144 DASH video 104k , webm container, vp9, 30fps, video only, 1.32MiB
160 mp4 256x144 DASH video 116k , avc1.4d400c, 30fps, video only, 1.53MiB
242 webm 426x240 DASH video 255k , vp9, 30fps, video only, 3.04MiB
133 mp4 426x240 DASH video 256k , avc1.4d4015, 30fps, video only, 3.37MiB
243 webm 640x360 DASH video 490k , vp9, 30fps, video only, 5.57MiB
134 mp4 640x360 DASH video 645k , avc1.4d401e, 30fps, video only, 7.85MiB
244 webm 854x480 DASH video 910k , vp9, 30fps, video only, 10.19MiB
135 mp4 854x480 DASH video 1170k , avc1.4d401f, 30fps, video only, 14.50MiB
247 webm 1280x720 720p 1550k , vp9, 30fps, video only, 20.09MiB
136 mp4 1280x720 720p 2331k , avc1.4d401f, 30fps, video only, 27.85MiB
302 webm 1280x720 DASH video 2731k , vp9, 60fps, video only, 34.08MiB
248 webm 1920x1080 1080p 2819k , vp9, 30fps, video only, 35.25MiB
298 mp4 1280x720 DASH video 3483k , avc1.4d4020, 60fps, video only, 41.24MiB
137 mp4 1920x1080 1080p 4393k , avc1.640028, 30fps, video only, 50.39MiB
303 webm 1920x1080 DASH video 4488k , vp9, 60fps, video only, 56.82MiB
299 mp4 1920x1080 DASH video 5889k , avc1.64002a, 60fps, video only, 70.59MiB
271 webm 2560x1440 1440p 9105k , vp9, 30fps, video only, 110.54MiB
264 mp4 2560x1440 DASH video 9401k , avc1.640032, 30fps, video only, 101.08MiB
308 webm 2560x1440 DASH video 13802k , vp9, 60fps, video only, 157.70MiB
313 webm 3840x2160 2160p 18658k , vp9, 30fps, video only, 232.08MiB
266 mp4 3840x2160 DASH video 23285k , avc1.640033, 30fps, video only, 269.17MiB
315 webm 3840x2160 DASH video 27682k , vp9, 60fps, video only, 345.88MiB
17 3gp 176x144 small , mp4v.20.3, mp4a.40.2@ 24k
36 3gp 320x180 small , mp4v.20.3, mp4a.40.2
43 webm 640x360 medium , vp8.0, vorbis@128k
18 mp4 640x360 medium , avc1.42001E, mp4a.40.2@ 96k
22 mp4 1280x720 hd720 , avc1.64001F, mp4a.40.2@192k (best)
该程序可以“合并”音频和视频吗？如果不能，可以使用 FFmpeg 自动执行该过程吗？
更新：我无意中youtube-dl -f best [URL]在只需要时使用了命令youtube-dl [URL]。FFmpeg 确实默认合并了音轨
答案1
如果您安装了 ffmpeg/avconv，它应该默认合并它们，但您可以强制它使用合并它们-f bestvideo+bestaudio。