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• How to broadcast a stream of Buffered Images to another computer over LAN network by using Java Core

  12 janvier 2017, par Trung Thanh Ngo

  I am working with raspberry pi 3 acting as a server which controls a Sony camera (HX400V model). I am able to use Sony Remote API to control the Pi to extract buffered images in the Sony camera’s liveview stream.

  I want to create and broadcast a stream of those buffered images to another computer over LAN network.

  I succeeded in sending those buffered images by using java socket but there was a delay of 2 seconds which is not good. The Pi acts as a socket client and the other computer acts as a socket server.

  Is there any way to create a stream and broadcast smoothly to another computer by using Java or anything else ?

• Why is there an audio delay on recording video stream with ffmpeg ?

  25 décembre 2023, par mqwerty

  I am trying to record video and audio stream (Line in Microphone Analog Audio) which are streaming from broadcaster computer with those parameters in the recorder computer ;

  


  ffmpeg record parameters :

  


  /usr/bin/ffmpeg -y -buffer_size max -thread_queue_size 8192 -i udp://225.0.5.11:1026 -buffer_size max -thread_queue_size 8192 -i udp://225.0.5.11:1032 -map 0:v -map 1:a -metadata title=COMPUTER-01_metadata_file -metadata creation_time="2023-12-25 13:25:29" -threads 0 -c:v copy -c:a copy -movflags +faststart -f segment -segment_time 01:00:00 -segment_atclocktime 1 -reset_timestamps 1 -strftime 1 -segment_format mp4 -t 120 test_record_video_with_audio_%Y-%m-%d_%H-%M-%S.mp4


  


  The ffmpeg started and finished successfully, but when I open the recorded video with mpv like (mpv test_record_video_with_audio.mp4), I realized that there is a 5-6 seconds delay in audio. How can I prevent the delay of audio in the recorded mp4 file without using offset ? My last option is setting offset but I think that it is not safe according to any changes in network or etc.

  


  FFMPEG version on both computer :

  


  ffmpeg version 4.2.9 Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 8 (GCC)


  


  BROADCASTER COMPUTER :

  


  sysctl.conf :

  


  No added configurations.


  


  ethtool output :

  


  Supported ports: [ TP ]
Supported link modes:   100baseT/Full
                        1000baseT/Full
                        10000baseT/Full
                        2500baseT/Full
                        5000baseT/Full
Supported pause frame use: Symmetric
Supports auto-negotiation: Yes
Supported FEC modes: Not reported
Advertised link modes:  100baseT/Full
                        1000baseT/Full
                        10000baseT/Full
Advertised pause frame use: Symmetric
Advertised auto-negotiation: Yes
Advertised FEC modes: Not reported
Speed: 10000Mb/s
Duplex: Full
Auto-negotiation: on
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
MDI-X: Unknown
Supports Wake-on: d
Wake-on: d
    Current message level: 0x00000007 (7)
                           drv probe link
Link detected: yes


  


  ffmpeg video stream :

  


  ffmpeg -fflags +genpts -f x11grab -framerate 30 -video_size uhd2160 -i :0 -c:v hevc_nvenc -preset fast -pix_fmt bgr0 -b:v 3M -g 25 -an -f mpegts udp://225.0.5.11:1026


  


  ffmpeg audio stream :

  


  ffmpeg -f alsa -i hw:0,0 -c:a aac -ar 48000 -b:a 1024K -ab 512k -f rtp_mpegts rtp://225.0.5.11:1032


  


  nvidia-smi :

  


  | NVIDIA-SMI 535.129.03             Driver Version: 535.129.03   CUDA Version: 12.2     |
|-----------------------------------------+----------------------+----------------------+
| GPU  Name                 Persistence-M | Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp   Perf          Pwr:Usage/Cap |         Memory-Usage | GPU-Util  Compute M. |
|                                         |                      |               MIG M. |
|=========================================+======================+======================|
|   0  NVIDIA T400 4GB                Off | 00000000:5B:00.0 Off |                  N/A |
| 38%   38C    P8              N/A /  31W |    207MiB /  4096MiB |      0%      Default |
|                                         |                      |                  N/A |
+-----------------------------------------+----------------------+----------------------+
|   1  NVIDIA RTX A4000               Off | 00000000:9E:00.0 Off |                  Off |
| 41%   59C    P2              41W / 140W |    766MiB / 16376MiB |     17%      Default |
|                                         |                      |                  N/A |
+-----------------------------------------+----------------------+----------------------+
                                                                                         
+---------------------------------------------------------------------------------------+
| Processes:                                                                            |
|  GPU   GI   CI        PID   Type   Process name                            GPU Memory |
|        ID   ID                                                             Usage      |
|=======================================================================================|
|    0   N/A  N/A      3227      G   /usr/libexec/Xorg                           114MiB |
|    0   N/A  N/A      3423      G   /usr/bin/gnome-shell                         87MiB |
|    1   N/A  N/A      3227      G   /usr/libexec/Xorg                           285MiB |
|    1   N/A  N/A      3423      G   /usr/bin/gnome-shell                         91MiB |
|    1   N/A  N/A      3762      C   ffmpeg                                      372MiB |
+---------------------------------------------------------------------------------------+


  


  lscpu output :

  


  

Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              96
On-line CPU(s) list: 0-95
Thread(s) per core:  2
Core(s) per socket:  24
Socket(s):           2
NUMA node(s):        2
Vendor ID:           GenuineIntel
BIOS Vendor ID:      Intel(R) Corporation
CPU family:          6
Model:               85
Model name:          Intel(R) Xeon(R) Gold 5220R CPU @ 2.20GHz
BIOS Model name:     Intel(R) Xeon(R) Gold 5220R CPU @ 2.20GHz
Stepping:            7
CPU MHz:             2200.000
CPU max MHz:         4000.0000
CPU min MHz:         1000.0000
BogoMIPS:            4400.00
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            1024K
L3 cache:            36608K
NUMA node0 CPU(s):   0-23,48-71
NUMA node1 CPU(s):   24-47,72-95


  


  OS : CentOS Stream release 8


  


  RECORDER COMPUTER :

  


  sysctl.conf :

  


  net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.tcp_rmem= 4096 87380 16777216
net.ipv4.tcp_wmem= 4096 65536 16777216
net.ipv4.tcp_window_scaling = 1
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_no_metrics_save = 0
net.core.netdev_max_backlog = 50000
net.core.optmem_max=25165824


  


  lscpu output :

  


  Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              96
On-line CPU(s) list: 0-95
Thread(s) per core:  2
Core(s) per socket:  24
Socket(s):           2
NUMA node(s):        2
Vendor ID:           GenuineIntel
BIOS Vendor ID:      Intel
CPU family:          6
Model:               106
Model name:          Intel(R) Xeon(R) Gold 5318Y CPU @ 2.10GHz
BIOS Model name:     Intel(R) Xeon(R) Gold 5318Y CPU @ 2.10GHz
Stepping:            6
CPU MHz:             3400.000
CPU max MHz:         3400.0000
CPU min MHz:         800.0000
BogoMIPS:            4200.00
Virtualization:      VT-x
L1d cache:           48K
L1i cache:           32K
L2 cache:            1280K
L3 cache:            36864K


  


  ethtool output :

  


  Supported ports: [ TP ]
    Supported link modes:   1000baseT/Full
                            10000baseT/Full
    Supported pause frame use: Symmetric Receive-only
    Supports auto-negotiation: Yes
    Supported FEC modes: Not reported
    Advertised link modes:  1000baseT/Full
                            10000baseT/Full
    Advertised pause frame use: Symmetric
    Advertised auto-negotiation: Yes
    Advertised FEC modes: Not reported
    Speed: 10000Mb/s
    Duplex: Full
    Auto-negotiation: on
    Port: Twisted Pair
    PHYAD: 12
    Transceiver: internal
    MDI-X: Unknown
    Supports Wake-on: d
    Wake-on: d
        Current message level: 0x00002081 (8321)
                               drv tx_err hw
    Link detected: yes


  


  No NVIDIA Graphic Driver

  


  OS : CentOS Stream release 8


  


  I tried audio encoding while recording like :

  


  "-c:a", "aac",  
"-ar", "48000", 
"-b:a", "128k",


  


  I also tried :

  


  "aresample=async=1"



  


  Unfortunately,these did not have any improvements on preventing latency in audio.

  


• Chrome’s New Audio Notifier

  30 janvier 2014, par Multimedia Mike — General

  Version 32 of Google’s Chrome web browser introduced this nifty feature :

  
  
  

  When a browser tab has an element that is producing audio, the browser’s tab shows the above audio notification icon to inform the user. I have seen that people have a few questions about this, specifically :

  1. How does this feature work ?
  2. Why wasn’t this done sooner ?
  3. Are other browsers going to follow suit ?

  Short answers : 1) Chrome offers a new plugin API that the Flash Player is now using, as are Chrome’s internal media playing facilities ; 2) this feature was contingent on the new plugin infrastructure mentioned in the previous answer ; 3) other browsers would require the same infrastructure support.

  Longer answers follow…

  Plugin History
  Plugins were originally based on the Netscape Plugin API. This was developed in the early 1990s in order to support embedding PDFs into the Netscape web browser. The NPAPI does things like providing graphics contexts for drawing and input processing, and mediate network requests through the browser’s network facilities.

  What NPAPI doesn’t do is handle audio. In the early-mid 1990s, audio support was not a widespread consideration in the consumer PC arena. Due to the lack of audio API support, if a plugin wanted to play audio, it had to go outside of the plugin framework.

  
  
  

  There are a few downsides to this approach :

  • If a plugin wants to play audio, it needs to access unique audio APIs on each supported platform. One of the most famous things I’ve ever written deals concerns this nightmare on Linux. (The picture worth a thousand words.)
  • Plugin necessarily needs free unrestricted access to system facilities, i.e., security measures like sandboxing become more difficult without restricting functionality.
  • Since the browser doesn’t mediate access to the audio APIs, the browser can’t reasonably be expected to know when a plugin is accessing the audio resources.

  So that last item hopefully answers the question of why it has been so difficult for NPAPI-supporting browsers to implement what seems like it would be simple functionality, like implementing a per-tab audio notifier.

  Plugin Future
  Since Google released Chrome in an effort to facilitate advancements on the client side of the internet, they have made numerous efforts to modernize various legacy aspects of web technology. These efforts include the SPDY protocol, Native Client, WebM/WebP, and something call the Pepper Plugin API (PPAPI). This is a more modern take on the classic plugin architecture to supplant the aging NPAPI :

  
  
  

  Right away, we see that the job of the plugin writer is greatly simplified. Where was this API years ago when I was writing my API jungle piece ?

  The Linux version of Chrome was apparently the first version that packaged the Pepper version of the Flash Player (doing so fixed an obnoxious bug in the Linux Flash Player interaction with GTK). Now, it looks like Windows and Mac have followed suit. Digging into the Chrome directory on a Windows 7 installation :

  AppData\Local\Google\Chrome\Application[version]\PepperFlash\pepflashplayer.dll

  This directory exists for version 31 as well, which is still hanging around my system.

  So, to re-iterate : Chrome has a new plugin API that plugins use to access the audio API. Chrome knows when the API is accessed and that allows the browser to display the audio notifier on a tab.

  Other Browsers
  What about other browsers ? “Mozilla is not interested in or working on Pepper at this time. See the Chrome Pepper pages.”