RTSP live stream not working in Home app
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**Describe The Problem:**
I have several IP cameras in my home. Some from Hikvision and some from Sercomm. Hikvision cameras are working fine but for some reason I can't make the Sercomm cameras live stream to work in the Home app when I use vcodec: "copy". I see the cameras I see the snapshots but once i try to start the live I see the loader for about a minute and after this I get "the camera is not responding".
Everything in the logs seems to be ok. I see the connection being started and the packets sent from homebridge to the phone.
I tried various solutions that i found online with no success.

When i remove vcodec: "copy" i can see the live stream in the home app.
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**Logs:**
<!-- Bug reports that do not contain logs may be closed without warning. -->

```
[info] Input #0, rtsp, from 'rtsp://username:pass@192.168.1.54:554/img/media.sav?stream=1':
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]   Metadata:
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]     title           : RTSP Server(H264) - OC452EB5BCD
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]   Duration: N/A, start: 0.194000, bitrate: N/A
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]     Stream #0:0: Video: h264 (Main), 1 reference frame, yuv420p(tv, bt709, progressive, left), 1920x1080 (1920x1088) [SAR 1:1 DAR 16:9], 25 fps, 30 tbr, 90k tbn, 50 tbc
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info] Output #0, rtp, to 'srtp://192.168.1.10:64971?rtcpport=64971&pkt_size=1316':
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]   Metadata:
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]     title           : RTSP Server(H264) - OC452EB5BCD
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]     encoder         : Lavf58.45.100
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]     Stream #0:0: Video: h264 (Main), 1 reference frame, yuv420p(tv, bt709, progressive, left), 1920x1080 (0x0) [SAR 1:1 DAR 16:9], q=2-31, 25 fps, 30 tbr, 90k tbn, 25 tbc
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info] Stream mapping:
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info]   Stream #0:0 -> #0:0 (copy)
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info] Press [q] to stop, [?] for help
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [rtp @ 0x3cb2100] [warning] Non-monotonous DTS in output stream 0:0; previous: 0, current: -17460; changing to 0. This may result in incorrect timestamps in the output file.
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [rtp @ 0x3cb2100] [warning] Non-monotonous DTS in output stream 0:0; previous: 0, current: -14400; changing to 0. This may result in incorrect timestamps in the output file.
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [rtp @ 0x3cb2100] [warning] Non-monotonous DTS in output stream 0:0; previous: 0, current: -11430; changing to 0. This may result in incorrect timestamps in the output file.
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [rtp @ 0x3cb2100] [warning] Non-monotonous DTS in output stream 0:0; previous: 0, current: -8460; changing to 0. This may result in incorrect timestamps in the output file.
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [rtp @ 0x3cb2100] [warning] Non-monotonous DTS in output stream 0:0; previous: 0, current: -2430; changing to 0. This may result in incorrect timestamps in the output file.
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] [info] frame=   21 fps=0.0 q=-1.0 size=     233kB time=00:00:00.57 bitrate=3330.1kbits/s speed=1.13x    
[01/08/2021, 14:02:11] [Camera FFmpeg] [Front Side] Getting the first frames took 1.854 seconds.
[01/08/2021, 14:02:12] [Camera FFmpeg] [Front Side] [info] frame=   33 fps= 33 q=-1.0 size=     353kB time=00:00:01.04 bitrate=2780.5kbits/s speed=1.03x
```

**Homebridge Config:**

```json
{
                    "name": "Front Side",
                    "motion": true,
                    "switches": false,
                    "motionTimeout": 15,
                    "unbridge": true,
                    "manufacturer": "Sercomm",
                    "videoConfig": {
                        "source": "-re -i rtsp://username:pass@192.168.1.54:554/img/media.sav?stream=1",
                        "stillImageSource": "-i http://username:pass@192.168.1.54/img/snapshot.cgi?size=5&quality=1",
                        "maxStreams": 2,
                        "maxWidth": 1920,
                        "maxHeight": 1080,
                        "maxFPS": 30,
                        "vcodec": "copy",
                        "audio": false,
                        "debug": true
                    }
                },
```

**Environment:**

* **Node.js Version**: v14.17.4
* **NPM Version**: v6.14.14
* **Homebridge Version**: 1.3.4
* **Homebridge Camera FFmpeg Version**: 3.1.2
* **Homebridge Config UI X Plugin Version**: 4.41.1
* **Operating System**: Raspbian GNU/Linux Buster (10)


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