udp - GStreamer UDPSink block 大小属性不起作用？

Question

我正在使用GStreamer并使用以下管道发送音频：

gst-launch-1.0 -v filesrc location=soundfile.mp3 ! mad ! audioconvert ! audio/x-raw, layout=interleaved, format=F32LE, channels=2 ! udpsink blocksize=512 port=5005 host=127.0.0.1

但是，blocksize似乎根本不起作用。这是udpsink的文档，可通过gst-inspect udpsink访问：

Element Properties:
  name                : The name of the object
                        flags: readable, writable
                        String. Default: "udpsink0"
  preroll-queue-len   : Number of buffers to queue during preroll
                        flags: readable, writable
                        Unsigned Integer. Range: 0 - 4294967295 Default: 0 
  sync                : Sync on the clock
                        flags: readable, writable
                        Boolean. Default: true
  max-lateness        : Maximum number of nanoseconds that a buffer can be late before it is dropped (-1 unlimited)
                        flags: readable, writable
                        Integer64. Range: -1 - 9223372036854775807 Default: -1 
  qos                 : Generate Quality-of-Service events upstream
                        flags: readable, writable
                        Boolean. Default: false
  async               : Go asynchronously to PAUSED
                        flags: readable, writable
                        Boolean. Default: true
  ts-offset           : Timestamp offset in nanoseconds
                        flags: readable, writable
                        Integer64. Range: -9223372036854775808 - 9223372036854775807 Default: 0 
  enable-last-buffer  : Enable the last-buffer property
                        flags: readable, writable
                        Boolean. Default: true
  last-buffer         : The last buffer received in the sink
                        flags: readable
                        MiniObject of type "GstBuffer"
  blocksize           : Size in bytes to pull per buffer (0 = default)
                        flags: readable, writable
                        Unsigned Integer. Range: 0 - 4294967295 Default: 4096 
  render-delay        : Additional render delay of the sink in nanoseconds
                        flags: readable, writable
                        Unsigned Integer64. Range: 0 - 18446744073709551615 Default: 0 
  throttle-time       : The time to keep between rendered buffers (unused)
                        flags: readable, writable
                        Unsigned Integer64. Range: 0 - 18446744073709551615 Default: 0 
  bytes-to-serve      : Number of bytes received to serve to clients
                        flags: readable
                        Unsigned Integer64. Range: 0 - 18446744073709551615 Default: 0 
  bytes-served        : Total number of bytes sent to all clients
                        flags: readable
                        Unsigned Integer64. Range: 0 - 18446744073709551615 Default: 0 
  sockfd              : Socket to use for UDP sending. (-1 == allocate)
                        flags: readable, writable
                        Integer. Range: -1 - 2147483647 Default: -1 
  closefd             : Close sockfd if passed as property on state change
                        flags: readable, writable
                        Boolean. Default: true
  sock                : Socket currently in use for UDP sending. (-1 == no socket)
                        flags: readable
                        Integer. Range: -1 - 2147483647 Default: -1 
  clients             : A comma separated list of host:port pairs with destinations
                        flags: readable, writable
                        String. Default: "localhost:4951"
  auto-multicast      : Automatically join/leave the multicast groups, FALSE means user has to do it himself
                        flags: readable, writable
                        Boolean. Default: true
  ttl                 : Used for setting the unicast TTL parameter
                        flags: readable, writable
                        Integer. Range: 0 - 255 Default: 64 
  ttl-mc              : Used for setting the multicast TTL parameter
                        flags: readable, writable
                        Integer. Range: 0 - 255 Default: 1 
  loop                : Used for setting the multicast loop parameter. TRUE = enable, FALSE = disable
                        flags: readable, writable
                        Boolean. Default: true
  qos-dscp            : Quality of Service, differentiated services code point (-1 default)
                        flags: readable, writable
                        Integer. Range: -1 - 63 Default: -1 
  send-duplicates     : When a distination/port pair is added multiple times, send packets multiple times as well
                        flags: readable, writable
                        Boolean. Default: true
  buffer-size         : Size of the kernel send buffer in bytes, 0=default
                        flags: readable, writable
                        Integer. Range: 0 - 2147483647 Default: 0 
  host                : The host/IP/Multicast group to send the packets to
                        flags: readable, writable
                        String. Default: "localhost"
  port                : The port to send the packets to
                        flags: readable, writable
                        Integer. Range: 0 - 65535 Default: 4951 

这已经有些令人困惑，因为 blocksize的默认值同时列出为0和4096。但是似乎它是4096，因为无论我为 blocksize使用什么值，这都是我的UDP数据包大小。更令人困惑的是，即使在GStreamer自己的文档中，我也几乎找不到在线任何地方提到的 blocksize属性： http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-good-plugins/html/gst-plugins-good-plugins-udpsink.html

提到的唯一属性是 host和 port。 blocksize是否已被弃用？如果可以，是否有任何方法可以控制每个UDP数据包中发送的数据量？我已经尝试过在RTP中使用mtu属性，但是没有运气（请参见此处： gstreamer RTP packet size），对此我颇有帮助。

Answer 1

在元素上使用gstinspect时，它会显示所有属性-不仅来自特定元素，还来自其父元素。这是真正的预期行为。

UdpSink实际上仅具有host和port属性。父级-GstMultiUDPSink还有更多。

您可以在GStreamer文档中以树的形式（对象层次结构段落）找到继承链。不幸的是，并非所有链接都能正常工作，因此最好为父元素使用Google适当的链接。

好了，回到问题上，您所提到的blocksize是GstBaseSink
的属性，并被描述为：


在拉模式下操作时要拉的字节数。
标志：读/写

默认值：4096


因此，它定义了它将从上游元素提取多少数据。它不会影响UDP数据包。您可能正在寻找的是buffer-size的GstMultiUDPSink属性：


“缓冲区大小”的闪光
内核发送缓冲区的大小（以字节为单位），0 =默认值。

标志：读/写

允许值：> = 0

默认值：0