Can't find the TV when casting on your phone, no sound when casting? I checked these three layers, and a 90% chance of a failure would be fixed in five minutes
night, my wife cast to her phone to watch shows. She opened the TV button and scrolled for ages, but the device list was empty, and she couldn't find a single device. Her phone had full signal and normal internet speed, so watching videos was smooth without any lag. I took it over and was amused—my phone was connected to the neighbor's WiFi upstairs, with the exact same name as my 2.4G. Her phone 'remembered' the neighbor's network in the middle of the night and automatically connected.
casting has all kinds of failures, but after I went through every TV, box, and speaker at home, I found that there are three layers of failure: not finding the device is the discovery layer's problem; casting with no picture but no sound is the format layer's problem; and the delivery layer is stuck as a PPT. Layered search, 90% of problems can be localized in five minutes.
first figure out which path you're betting on—three paths have three different things
many people think casting means "the phone sends the screen over," but actually, the casting button on the phone does something different from what you might think. I split it into three roads and said:
the first way: the TV button in the online video app. the small TV icon on the playback page of Tencent, iQIYI, or Bilibili, click on the device selection, and what it does is send the playback address to the TV, then the TV itself to streaming. From start to finish, the phone is just a remote control; once you lock the screen, exit the app, or even step outside, the TV continues playing. So whether the casting card is laggy has nothing to do with the phone signal at all—it's the TV's own network issue.
second option: Casting local files. videos from your phone's album and movies from your NAS are pushed to the TV via DLNA. This is the real way to push video streaming from your phone or NAS to your TV, using home WiFi and taking up your home bandwidth.
Third Way: Screen Mirroring. copy the entire phone screen onto the TV, playing games or holding video conferences frequently. Most Android "wireless screen casting" uses Miracast, connecting phones and TVs point-to-point without taking up any home router bandwidth; The common LeBo solution on domestic TVs essentially involves recording the phone screen with encoding and streaming later, which causes the phone to overheat and the picture quality suffers.
| failure shows | the faulty layer | in a single sentence direction |
| the device list is empty or the | cannot be found | Phones and TVs are not in the same 'circle of friends' |
| with images without sound, black screens, gray buttons | format layers audio track and subtitle copyrights causing trouble | |
| the transmission layer is stuck but stuck PPT | the transport layer | first distinguish who is pulling traffic |
First Layer: No equipment found, five real culprits are identified by probability
True Culprit One: Mobile phones and TVs are not on the same network. this is the most common issue; mine was one of those times. Besides cases where people connect to the wrong network under the same name (I later renamed my WiFi at home, which I wrote about in the about changing WiFi names in ), there are two other types: one is when the phone connects to Guest Network —my relative stayed for a few days, I turned on the guest WiFi I enabled, and my wife casually connected her phone. The guest network is automatically isolated from the main network, devices can't see each other, and casting the screen naturally causes confusion, What can and cannot be done by the visitor network I've tested it—NAS and screen casting are completely unreachable; Another is that the TV is connected to the fiber modem's WiFi, and the phone is connected to the router's WiFi. Both network segments can't find each other. Remember this: under the same router, connecting your phone to 5G and your TV to 2.4G doesn't count as cross-network you can detect each other—don't believe the online claim that 'casting must be on the same band.'
True Culprit 2: AP isolation active. router has a switch in the background for "AP isolation" or "Wireless user interconnection." Once enabled, devices on the same WiFi connect and are invisible. This switch is normally off by household use, but I've seen second-hand routers and landlord-installed routers with it on. I've written a complete check what AP isolation is and where the different brands of switches are.
Culprit 3: The TV's reception program was not properly installed. Android TVs need to be used as the casting receiver, they need a corresponding app running. After upgrading the system on an old TV or clearing the background apps like "Casting and Reception" on the TV, it won't appear in the list. Check the TV app list—if it's not available, install one.
Culprit Four: TV is fake online. after the TV turns off and goes to sleep, the DLNA discovery service disconnects, but sometimes the phone's name is cached in the list, and clicking it doesn't respond or reports connection failure. First, use the remote to fully wake up the TV, wait for a dozen seconds before turning it on.
Culprit Five: Group broadcast blocked casting relies on detection protocols like SSDP and mDNS that use multicast. If your home network has been scanned via VLAN or done fine isolation, if multicast doesn't get through, you won't be able to detect it. Ordinary households can't encounter this rule; only those who have tried soft router partitioning are suspicious. multicast is explained the principle.
second layer: Projecting has images but no sound, the format is messing up
this layer is the most confusing, because the words "cast" make people think they've succeeded, but the characters in the drama don't speak. I rank them in the order I have stepped on:
DTS and AC3 audio track TVs are not accepted. I ran an old movie from my NAS to the TV. The picture was fine, but there was no sound. The audio file itself wasn't corrupted, but the TV wouldn't decode this audio track. This isn't the fault of screen casting; direct TV playback is just as mute— the about the movie where the TV plays directly on NAS, I detailed this pitfall and solutions, like changing audio tracks or changing players.
No external subtitles. DLNA streaming only promotes the video itself; the SRT subtitles hanging next to the phone won't follow, and the TV content is just raw content. You either push the subtitles into the video, or install a player on the TV that can load subtitles.
copyrighted content is directly banned from being invested. some series, due to copyright holder requirements, have the casting button grayed out or prompted "Casting is not supported due to copyright reasons." This is a limitation at the content level; no matter how good your home internet is, it won't help.
member resolution limits. this is an old grudge: starting January 2023, iQIYI lowered the casting resolution for Gold members to 480P. To cast in high definition, users had to upgrade to the more expensive Platinum membership, which led to user lawsuits. In July 2024, the court lost the platform in the first trial. Nowadays, each company's policies vary. Tencent Video is the most lenient, basically removing casting resolution restrictions, leaving only some copyrighted content unavailable. So if the casting quality suddenly blurs, first check if it's due to your membership level—don't rush to blame the router.
| symptoms | root | |
| with visuals but no sound | DTS/AC3 audio track | change audio tracks or player |
| if there are no subtitles | DLNA no external subtitles | subtitles are embedded into the video or TV player |
| Casting button is gray | copyright ban on casting | switch to TV app to watch or abandon it |
| image quality blurs 480P | membership restrictions | check member benefits or switch platforms |
Third layer: Turn it into a PPT, first distinguish who is pulling the stream
Before
check the check, ask first: Are you investing online or local?
online casting cards, check the TV, not the phone. As mentioned earlier, after pressing the TV button, the TV downloads videos automatically; a full phone signal doesn't help at all. My wife got stuck on her show. The first thing I did wasn't restart the router, but the WiFi for watching TV—the TV in the living room was separated from the router by a wall, with a 2.4G signal below -70dBm, and it would lag during the evening rush hour. Move the TV closer, connect it to 5G, or if that doesn't work, drag the network cable — this is more effective than anything else. TV connected to WiFi or plugged into an internet cable I tested the same show, and with the same show, moving the TV from the 2.4G edge to the 5G short-range range can increase bitrates several times over.
local casting card to calculate the bandwidth bill. local streaming really requires moving video data from your phone or NAS to your TV. 1080P sources generally require a sustained speed of around 8MB, while 4K original discs can reach 600MB or even higher. The phone is at the edge of 2.4G, negotiated at 72M, but in actual hands-on hands it usually only gets about 20MB, barely 1080P is enough, and 4K is sure to lag. This signal segmentation and bitrate ledger has been written in the on how to choose between 2.4G and 5G. If the signal is decent but still lags, and it lags at 8 or 9 PM, that's a channel collision. How do you choose channel scan the surroundings with your phone.
unsure where the bottleneck is, first run a speed test for the TV: if the TV measures above 20 to 30 Mbps, 1080P online is sufficient; Speaking of local 4K, that one should aim for hundreds of Mbps. One more thing: to safely promote local streaming, play videos on NAS and TV on TV, with every hop path wide enough. NAS push music to speakers same principle: source-to-end direct delivery, intermediate devices only forward.
iPhone and Android screen casting are not the same thing
Apple has two sets, and many people mix and use them thinking they're the same: the AirPlay button in the app, which focuses on video and saves power for stable picture quality; The 'screen mirroring' in Control Center copies the entire screen—whatever the phone does or the TV shows. If the TV doesn't have AirPlay certification (most domestic brands don't), you'll need to install a receiver app on the TV so your phone can see it in the list.
Android's "wireless screen casting" uses Miracast, allowing direct connection between phone and TV. The advantage is that it doesn't take up your home router's bandwidth and doesn't affect the router lag. The downside is that some app content will go black and won't be cast, which is an anti-recording mechanism. Apps like LeBo on TV that use casting apps like LeBo for QR code pairing rely on screen recording and streaming, so you can send anything, but the phone gets hot, the picture quality is degraded, there's a delay of just a fraction of a second, and it's not good for watching dramas or gaming.
the easiest way to cast to a computer is the browser casting plugin, which uses DLNA and works on the same principle as casting online videos on your phone.
according to the numbers, follow this order to check for the fastest
| your situation | first check that the |
| device list is empty | which WiFi your phone is connected to, which TV is connected to WiFi |
| is in the list. If you click the isolator switch and | AP it can't connect, check if the TV is online |
| cast | a silent audio track format, try switching to another track |
| online casting card | the TV network, relocating or switching frequency bands |
| local casting card | signal segmentation plus bandwidth account, 2.4G 5G |
finish with a clear order: first confirm your phone and TV are on the same network, then check the isolation switch; third, use the remote to wake up the TV and re-play it; fourth, check audio track subtitles; fifth, switch to network. The first three steps cost nothing, and 90% of casting failures can be solved. That time, my wife "forgot" the neighbor's network on her phone's WiFi, and the TV immediately appeared in the list.
