Is it normal that b[height<=480] gives me a better quality video than b[filesize<25M] ?

[Nicolas-Gth]

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Please make sure the question is worded well enough to be understood

I'm downloading this video : https://www.youtube.com/watch?v=SjgMmo6_DH0

The b[filesize<25M] setting give me a 2Mb mp4 with really low quality audio and the video is only the first frame. It's also quite slow when downloading.

But b[height<=480] gives me a decent 480p 8Mb mp4 file with good audio

Edit : b[height<=720] gives me a 21.73MiB file so I don't understand why b[filesize<25M] does not give me a similar result

Provide verbose output that clearly demonstrates the problem

• Run your yt-dlp command with -vU flag added (yt-dlp -vU <your command line>)
• If using API, add 'verbose': True to YoutubeDL params instead
• Copy the WHOLE output (starting with [debug] Command-line config) and insert it below

Complete Verbose Output

No response

[bashonly]

you are getting format 18 with b[height<=480], which only has an approximate (~) filesize available (filesize_approx) and is excluded if you filter by filesize

[info] Available formats for SjgMmo6_DH0:
ID  EXT   RESOLUTION FPS CH │   FILESIZE   TBR PROTO │ VCODEC          VBR ACODEC      ABR ASR MORE INFO
────────────────────────────────────────────────────────────────────────────────────────────────────────────────
sb2 mhtml 48x27        0    │                  mhtml │ images                                  storyboard
sb1 mhtml 80x45        1    │                  mhtml │ images                                  storyboard
sb0 mhtml 160x90       1    │                  mhtml │ images                                  storyboard
139 m4a   audio only      2 │    1.35MiB   49k https │ audio only          mp4a.40.5   49k 22k low, m4a_dash
249 webm  audio only      2 │    1.31MiB   47k https │ audio only          opus        47k 48k low, webm_dash
250 webm  audio only      2 │    1.73MiB   63k https │ audio only          opus        63k 48k low, webm_dash
140 m4a   audio only      2 │    3.58MiB  129k https │ audio only          mp4a.40.2  129k 44k medium, m4a_dash
251 webm  audio only      2 │    3.41MiB  123k https │ audio only          opus       123k 48k medium, webm_dash
17  3gp   176x144     12  1 │    2.05MiB   74k https │ mp4v.20.3       74k mp4a.40.2       22k 144p
394 mp4   256x144     24    │    1.85MiB   67k https │ av01.0.00M.08   67k video only          144p, mp4_dash
160 mp4   256x144     24    │    1.42MiB   51k https │ avc1.4d400c     51k video only          144p, mp4_dash
278 webm  256x144     24    │    2.28MiB   83k https │ vp9             83k video only          144p, webm_dash
395 mp4   426x240     24    │    2.96MiB  107k https │ av01.0.00M.08  107k video only          240p, mp4_dash
133 mp4   426x240     24    │    2.95MiB  107k https │ avc1.4d4015    107k video only          240p, mp4_dash
242 webm  426x240     24    │    3.46MiB  125k https │ vp9            125k video only          240p, webm_dash
396 mp4   640x360     24    │    5.37MiB  194k https │ av01.0.01M.08  194k video only          360p, mp4_dash
134 mp4   640x360     24    │    5.36MiB  194k https │ avc1.4d401e    194k video only          360p, mp4_dash
18  mp4   640x360     24  2 │ ~  9.14MiB  323k https │ avc1.42001E    323k mp4a.40.2       44k 360p
243 webm  640x360     24    │    6.82MiB  247k https │ vp9            247k video only          360p, webm_dash
397 mp4   854x480     24    │    8.93MiB  323k https │ av01.0.04M.08  323k video only          480p, mp4_dash
135 mp4   854x480     24    │   10.15MiB  367k https │ avc1.4d401e    367k video only          480p, mp4_dash
244 webm  854x480     24    │   11.23MiB  406k https │ vp9            406k video only          480p, webm_dash
22  mp4   1280x720    24  2 │ ~ 22.26MiB  786k https │ avc1.64001F    786k mp4a.40.2       44k 720p
398 mp4   1280x720    24    │   16.58MiB  600k https │ av01.0.05M.08  600k video only          720p, mp4_dash
136 mp4   1280x720    24    │   18.16MiB  657k https │ avc1.4d401f    657k video only          720p, mp4_dash
247 webm  1280x720    24    │   20.32MiB  735k https │ vp9            735k video only          720p, webm_dash
399 mp4   1920x1080   24    │   27.94MiB 1010k https │ av01.0.08M.08 1010k video only          1080p, mp4_dash
137 mp4   1920x1080   24    │   41.19MiB 1490k https │ avc1.640028   1490k video only          1080p, mp4_dash
248 webm  1920x1080   24    │   34.27MiB 1239k https │ vp9           1239k video only          1080p, webm_dash
400 mp4   2560x1440   24    │   81.98MiB 2965k https │ av01.0.12M.08 2965k video only          1440p, mp4_dash
271 webm  2560x1440   24    │   82.14MiB 2971k https │ vp9           2971k video only          1440p, webm_dash
401 mp4   3840x2160   24    │  174.88MiB 6325k https │ av01.0.12M.08 6325k video only          2160p, mp4_dash
313 webm  3840x2160   24    │  270.87MiB 9797k https │ vp9           9797k video only          2160p, webm_dash

[Nicolas-Gth]

So what should I use instead ? Something like b[filesize~24M] ?

[bashonly]

filesize_approx is what would filter the formats with only approximate filesizes

the easiest solution would be to use format sorting instead of format selection filtering, like -f b -S size:24M , since it sorts by both filesize and approximate filesize

[Nicolas-Gth]

Thank you !

[gamer191]

the easiest solution would be to use format sorting instead of format selection filtering, like -f b -S size:24M

I would just do -S size:24M. -f b shouldn't be used unless you know what it does (hint: it doesn't download the best quality)

[Nicolas-Gth]

ydl_opts = {
		'format': 'b[ext=mp4]',
		'format_sort' : 'size:25M',
		'outtmpl': f'{folderPath}{mp4_title}.mp4',
		'ffmpeg_location': './ffmpeg-N-103380-ge41bd075dd-win64-gpl/bin/ffmpeg.exe',
		'noplaylist': True,
		'progress_hooks': [self.my_hook],
		'cachedir': False,
		'cookiefile' : cookiePath
		}

ERROR: Invalid format sort string ":" given by extractor

how should I write it ?

[bashonly]

'format_sort': ['size:25M']

use this to convert CLI to API https://github.com/yt-dlp/yt-dlp/blob/master/devscripts/cli_to_api.py

[Nicolas-Gth]

the easiest solution would be to use format sorting instead of format selection filtering, like -f b -S size:24M

I would just do -S size:24M. -f b shouldn't be used unless you know what it does (hint: it doesn't download the best quality)

Can you explain please ?

[gamer191]

-f b is used to limit yt-dlp to combined video+audio formats. It's not recommended, since the non-combined formats are usually much higher quality, and, assuming you have ffmpeg installed, yt-dlp will automatically merge the best quality video and audio formats matching your options

[bashonly]

and if you want to heed gamer191's advice, additionally I would suggest not using a format param at all in your opts.
instead you could only use format sorting, like this:
{'format_sort': ['ext', 'size:25M']}
it will sort formats by extension (mp4 having priority) and then by size (formats with a size of 25M or less having priority)

[Nicolas-Gth]

Ok thanks, the only problem is that it seems that the 'size:25M' only looks at the files separately so once the mp4 and m4a are combined the file is more than 25Mb

[gamer191]

@ThurstyWonk the audio is usually pretty small (3.41MiB in your example video), but yes, that is a known limitation (see #4846). If that's a problem, you'll need to add back -f b