On Thursday, 18 April 2019 03:43:05 BST Walter Dnes wrote: > This thread has piqued my interest in youtube-dl. I'm trying to get > best audio and video together in a 1920x1080 video for Youtube URL > https://www.youtube.com/watch?v=A9tKncAdlHQ > > My config file is... > > -f bestvideo[width<=1920]+bestaudio > --merge-output-format mp4
Best audio available may not be compatible with an mp4 container without some manual conversion - see below. > --no-mtime > --no-playlist > -o ~/ytdl/%(title)s.%(ext)s > --restrict-filenames > > If I use "-f bestvideo[width<=1920]" I get a 1920x1080 video...with no > sound. Yes, because this is what you asked - video stream only. > If I use "-f best[width<=1920]" I get a 1280x720 video with > sound. Yes, this will download a *single* container file which contains both video and audio pre-muxed streams, with the best quality video size of less or equal to 1920px in width. Youtube has a 720p single file available containing both audio and video, so this is selected. > That works, but I want the best of both worlds. With > "-f bestvideo[width<=1920]+bestaudio", ffmpeg fails... > > [i660][waltdnes][~/ytdl] youtube-dl > https://www.youtube.com/watch?v=A9tKncAdlHQ [youtube] A9tKncAdlHQ: > Downloading webpage > [youtube] Downloading just video A9tKncAdlHQ because of --no-playlist > [download] Destination: > /home/waltdnes/ytdl/Double_Slit_Experiment_explained_by_Jim_Al-Khalili.f137 > .mp4 [download] 100% of 31.55MiB in 00:17 > [download] Destination: > /home/waltdnes/ytdl/Double_Slit_Experiment_explained_by_Jim_Al-Khalili.f251 > .webm [download] 100% of 6.65MiB in 00:03 > [ffmpeg] Merging formats into > "/home/waltdnes/ytdl/Double_Slit_Experiment_explained_by_Jim_Al-Khalili.mp4 > " ERROR: Stream #1:0 -> #0:1 (copy) > > Any idea what's wrong? Looking at the above output and also taking a look at the formats available for download: $ youtube-dl -F 'https://www.youtube.com/watch?v=A9tKncAdlHQ' [youtube] A9tKncAdlHQ: Downloading webpage [youtube] A9tKncAdlHQ: Downloading video info webpage [info] Available formats for A9tKncAdlHQ: format code extension resolution note 249 webm audio only DASH audio 54k , opus @ 50k, 3.24MiB 250 webm audio only DASH audio 71k , opus @ 70k, 3.62MiB 140 m4a audio only DASH audio 128k , m4a_dash container, mp4a.40.2@128k, 8.29MiB 171 webm audio only DASH audio 133k , vorbis@128k, 6.09MiB 251 webm audio only DASH audio 137k , opus @160k, 6.65MiB 278 webm 256x144 144p 96k , webm container, vp9, 25fps, video only, 4.42MiB 160 mp4 256x144 144p 112k , avc1.4d400c, 25fps, video only, 2.09MiB 242 webm 426x240 240p 224k , vp9, 25fps, video only, 5.26MiB 133 mp4 426x240 240p 268k , avc1.4d4015, 25fps, video only, 4.72MiB 243 webm 640x360 360p 404k , vp9, 25fps, video only, 11.51MiB 134 mp4 640x360 360p 616k , avc1.4d401e, 25fps, video only, 9.64MiB 244 webm 854x480 480p 678k , vp9, 25fps, video only, 20.51MiB 135 mp4 854x480 480p 1186k , avc1.4d401e, 25fps, video only, 15.17MiB 247 webm 1280x720 720p 1328k , vp9, 25fps, video only, 26.90MiB 136 mp4 1280x720 720p 2037k , avc1.4d401f, 25fps, video only, 22.90MiB 248 webm 1920x1080 1080p 2349k , vp9, 25fps, video only, 34.44MiB 137 mp4 1920x1080 1080p 2710k , avc1.640028, 25fps, video only, 31.55MiB 18 mp4 640x360 medium , avc1.42001E, mp4a.40.2@ 96k, 23.30MiB 43 webm 640x360 medium , vp8.0, vorbis@128k, 28.60MiB 22 mp4 1280x720 hd720 , avc1.64001F, mp4a.40.2@192k (best) we can see you downloaded formats .f137 and .f251. The 137 file is a 1080p video only file within an mp4 container. The 251 file is an opus audio file within a webm container. If you do not specify an output format for youtube-dl to transcode the video and audio into, the application will use a matroska container: [ffmpeg] Merging formats into "Double Slit Experiment explained! by Jim Al- Khalili-A9tKncAdlHQ.mkv" which will retain the best video with the size you requested as h264 *and* the best audio it could find as opus. This will adhere to your request for a best video and best audio. I do not think it would be logical for youtube-dl to transcode the audio from opus to aac, which is a suitable format for an mp4 container. For this you would need to specify manually the bitrate to be used by m4a and potentially other parameters to suit your preferences and then wait for ffmpeg to transcode the audio, which on a large download would take a while. It would be more logical to specify a suitable audio format for the container you intend to use upfront and ytdl would fetch this without any expensive post- processing. I suppose the devs could introduce a simple test to flag alternative audio formats available for download, which would be compatible with an mp4 container, instead of blindly downloading the opus stream and then ffmpeg failing to copy it into mp4. I assume the ytdl extractor logic is not linked into the post-processing ffmpeg logic (two separate stages) and this is why it errors out in the fashion you experienced. On a practical level, if the mkv container is not suitable for you, you could instead restrict the audio format to m4a and then ytdl will download the .f140 file rather than .f251 and mux video and audio into an mp4 container - but arguably this won't represent the 'best' audio. -- Regards, Mick
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