ytdl_hook fails due to large amounts of JSON data

Important Information

Provide following Information:

• mpv version

mpv 0.35.1-dirty Copyright © 2000-2023 mpv/MPlayer/mplayer2 projects
 built on Wed Mar 22 08:19:26 2023
FFmpeg library versions:
   libavutil       58.2.100
   libavcodec      60.3.100
   libavformat     60.3.100
   libswscale      7.1.100
   libavfilter     9.3.100
   libswresample   4.10.100
FFmpeg version: n6.0

• Linux Distribution and Version

Arch. uname -a:

Linux archfx 6.2.10-arch1-1 #1 SMP PREEMPT_DYNAMIC Fri, 07 Apr 2023 02:10:43 +0000 x86_64 GNU/Linux

• Source of the mpv binary

Official pacman repositories. pacman -Qi mpv:

Name            : mpv
Version         : 1:0.35.1-4
Description     : a free, open source, and cross-platform media player
Architecture    : x86_64
URL             : https://mpv.io/
Licenses        : GPL3
Groups          : None
Provides        : libmpv.so=2-64
Depends On      : alsa-lib  libasound.so=2-64  desktop-file-utils  ffmpeg  libavcodec.so=60-64  libavdevice.so=60-64
                  libavfilter.so=9-64  libavformat.so=60-64  libavutil.so=58-64  libswresample.so=4-64  libswscale.so=7-64  glibc
                  hicolor-icon-theme  jack  libjack.so=0-64  lcms2  liblcms2.so=2-64  libarchive  libarchive.so=13-64  libass
                  libass.so=9-64  libbluray  libbluray.so=2-64  libcdio  libcdio-paranoia  libdrm  libdvdnav  libdvdread  libegl  libgl
                  libglvnd  libjpeg  libjpeg.so=8-64  libplacebo  libplacebo.so=229-64  libpulse  libpulse.so=0-64  libva
                  libva.so=2-64  libva-drm.so=2-64  libva-wayland.so=2-64  libva-x11.so=2-64  libvdpau  libx11  libxext  libxinerama
                  libxkbcommon  libxkbcommon.so=0-64  libxpresent  libxrandr  libxss  libxv  luajit  mesa  mujs  libpipewire
                  rubberband  librubberband.so=2-64  shaderc  libshaderc_shared.so=1-64  uchardet  vulkan-icd-loader  wayland  zlib
Optional Deps   : yt-dlp: for video-sharing websites playback [installed]
                  youtube-dl: for video-sharing websites playback
Required By     : None
Optional For    : anki-bin
Conflicts With  : None
Replaces        : None
Installed Size  : 6.09 MiB
Packager        : Christian Hesse <eworm@archlinux.org>
Build Date      : Wed 22 Mar 2023 20:19:26 GMT
Install Date    : Fri 24 Mar 2023 20:03:58 GMT
Install Reason  : Explicitly installed
Install Script  : No
Validated By    : Signature

• If known which version of mpv introduced the problem

Unknown - I was watching similar videos yesterday, and with no system changes, this video I found today doesn't work.

• Window Manager and version

i3wm. i3 -v:

i3 version 4.22 (2023-01-02) © 2009 Michael Stapelberg and contributors

• GPU driver and version

amdgpu. Snipped lspci -v:

09:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] (rev e7) (prog-if 00 [VGA controller])
	Subsystem: Sapphire Technology Limited Nitro+ Radeon RX 570/580/590
	Flags: bus master, fast devsel, latency 0, IRQ 69, NUMA node 0
	Memory at c0000000 (64-bit, prefetchable) [size=256M]
	Memory at d0000000 (64-bit, prefetchable) [size=2M]
	I/O ports at b000 [size=256]
	Memory at fe400000 (32-bit, non-prefetchable) [size=256K]
	Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: amdgpu
	Kernel modules: amdgpu

• Possible screenshot or video of visual glitches

Not relevant.

Reproduction steps

Issue persists with --no-config.

• install mpv and yt-dlp;
• ensure yt-dlp 'https://www.youtube.com/watch?v=7Ip-zi-C66s' works and cancel it once you see it starting to download;
• run mpv 'https://www.youtube.com/watch?v=7Ip-zi-C66s'

Expected behavior

• mpv draws a window and plays a video

Actual behavior

• ytdl_hook fails with an error

[ytdl_hook]  
[ytdl_hook] youtube-dl failed: failed to parse JSON data: error 
Failed to recognize file format.

Exiting... (Errors when loading file)

Log file

output.txt (large)

Sample files

Not needed.

---

I notice that the amount of JSON ytdl_hook spits to the console is immense, and ends halfway through a string, breaking the JSON format. I also notice that the log file is suspiciously close to 64MiB in size. I am of course but a stupid idiot, but I wonder if there's something in ytdl_hook that's truncating something to that size, and this video for some reason overruns that limit.

Please note that mpv 'https://www.youtube.com/watch?v=aKNQPhVucVY' works fine so it's not all youtube videos, and mpv 'https://www.youtube.com/watch?v=k-9keDEstMg' works fine too, so it's not even live streams or recent live streams or stream archives that are the issue.

Start with the ytdl_hook entry point and reproduce the failure using the provided YouTube URL, yt-dlp, and the linked output.txt log. Inspect where the large JSON response is handled and whether the observed 64 MiB boundary is involved. Done means mpv can load and play this video without a JSON parsing or file-format error.