CCTV videos download without initial I frame? (so QT Player will not play, VLC renders only "semi-scrambled" P-frames?

[Jimw338]

Your question

URL: https://music.cctv.com/2021/12/31/VIDEmCMlEL32BjgO3UrTn8oG211231.shtml
URL 2: https://music.cctv.com/2023/07/03/VIDEWC6yLdA18xwwSqjt8rkH230703.shtml

This seems to download without an initial I frame, so only the "scrambled diff data" is rendered by when played in VLC (macOS M1 MBP, 3.0.21). Quicktime Player seems hit or miss whether it wants to render anything ("typical Apple.. Try to give correct behavior, or give you NOTHING").

The actual video appears to be a _video_player_html5_api blob AND and M3U8 file as a sub-element to that..

But Firefox (134.0) plays it fine in-browser. I assume this is an error on the server side. Could the FF decoding algorithm using the poster image itself as the initial P frame?

Addon & CoApp version and details

version: 9.1.0.44
target: mozilla
channel: stable
lang: en-US
coapp: {"found":true,"path":"/Applications/net.downloadhelper.coapp.app/Contents/MacOS/vdhcoapp","version":"2.0.19","new_version":false}
license: {"accepted":true,"email":"","key":"6a9555e39c3d4548"}
platform: aarch64 mac
UA: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:134.0) Gecko/20100101 Firefox/134.0
{
"valid_license_message_has_been_displayed": true,
"used_history_button": true,
"download_directory": "/Users/jswitte/dwhelper",
"last_download_directory": {
"__serializer_tag": "option_some",
"__serializer_value": {
"__serializer_tag": "primitive",
"__serializer_value": "/Users/jswitte/dwhelper"
}
},
"never_show_no_incognito_msg_again": true,
"view_options": {
"all_tabs": false,
"low_quality": false,
"sort_by_status": true,
"sort_reverse": false,
"show_button_clean": true,
"show_button_clean_all": false,
"show_button_convert_local": false,
"hide_downloaded": false
},
"use_legacy_ui": false,
"use_sidebar": false,
"open_count_store": 30,
"successfull_dl": 87,
"never_show_successfull_dl_message": true,
"download_history": {
"__serializer_tag": "map",
"__serializer_value": [
{
"__serializer_tag": "array",
"__serializer_value": [
{
"__serializer_tag": "primitive",
"__serializer_value": "downloadable_5391837648701464"
},
{
"download_result": {
"inbrowser": {
"__serializer_tag": "primitive",
"__serializer_value": false
},
"filepath": {
"__serializer_tag": "primitive",
"__serializer_value": "/Users/jswitte/dwhelper/国家大剧院声如夏花系列新时代经典作品音乐会灯火里的中国 演唱周深.mp4"
},
"filename": {
"__serializer_tag": "primitive",
"__serializer_value": "国家大剧院声如夏花系列新时代经典作品音乐会灯火里的中国 演唱周深.mp4"
},
"filedir": {
"__serializer_tag": "primitive",
"__serializer_value": "/Users/jswitte/dwhelper"
},
"qrcode": {
"__serializer_tag": "primitive",
"__serializer_value": false
}
},
"page_url": {
"__serializer_tag": "primitive",
"__serializer_value": "https://music.cctv.com/2023/07/03/VIDEE2U0rC8XMSbbwRG8LknZ230703.shtml"
},
"timestamp": {
"__serializer_tag": "primitive",
"__serializer_value": 1736782653563
}
}
]
}
]
},
"record_download_history": true
}¡

[GrampaWildWilly]

I do not work for VDH. I'm just another user.

I'm running Windows 11 Pro 64-bit version 24H2 build 26100.2605, Firefox 134.0 64-bit, licensed VDH 9.1.0.41 beta, CoApp 2.0.20.

For your first URL, VDH downloaded it apparently just fine. But as you said, it was scrambled. The audio seemed fine but the video was useless. So I downloaded it with ffmpeg directly:

Chinese Choir #1 mp4 Log.txt

There's a LOT of corrupt packets in this. This may amount to stealth DRM. I tried reencoding the file but it made no difference:

ffmpegCloneSceneLogFile.txt

For your second URL, VDH did the same thing: scrambled video, OK audio. When I tried to inspect the HLS master manifest, I got a 403 Forbidden. Twice. With these 403 errors, you should always try it twice. Some web sites cause their manifests to time out very quickly so it's always best to reload the page & try again. But I got 403 both times. That is stealth DRM. I'm surprised VDH downloaded anything in this case but there's a lot of things I don't understand.

This content is not protected by standard DRM. That means you should be able to use a screen recorder to make a copy of these videos. That's not as good as downloading but it looks like your only alternative here.

I don't know what the deal is here. Since the videos do play just fine in the browser window, I would surmise that the packets are not so much corrupt as that this web site has used some sort of non-standard video encoding technique. I have encountered content that was encrypted, but in those cases, the stream manifests referred to a key file. There are no such references to key files here. So again, I don't know how the browser is able to play the content but it can't be downloaded. This could be an intentional trick the web devs on that site have used to prevent downloading. It could be, as I said earlier, that they're using some non-standard video encoding. Whatever the case, this won't download.

[Mattmjs]

It looks like they have a way to implement DRM and it doesn't need the browser to have DRM enabled. Well actually I checked my
settings and DRM was turned on. I normally leave it off. So for this site you don't get the DRM icon to appear in Firefox.
But since I was probing around in developer tools there is a stream link that can be used, the trade off is it's only 240p.
If this is worth considering then I can share more information but if you want higher quality then you're out of luck here.