gstreamer/ext/avtp/meson.build

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avtp_sources = [
'gstavtp.c',
'gstavtpaafdepay.c',
avtp: Introduce AAF payloader element This patch introduces the AVTP Audio Format (AAF) payloader element from the AVTP plugin. The element inputs audio raw data and outputs AVTP packets (aka AVTPDUs), implementing a typical protocol payloader element from GStreamer. AAF is one of the available formats to transport audio data in an AVTP system. AAF is specified in IEEE 1722-2016 section 7 and provides two encapsulation mode: PCM and AES3. This patch implements PCM encapsulation mode only. The AAF payloader working mechanism consists of building the AAF header, prepending it to the GstBuffer received on the sink pad, and pushing the buffer downstream. Payloader parameters such as stream ID, maximum transit time, time uncertainty, and timestamping mode are passed via element properties. AAF doesn't support all possible sample format and sampling rate values so the sink pad caps template from the payloader is a subset of audio/x-raw. Additionally, this patch implements only "normal" timestamping mode from AAF. "Sparse" mode should be implemented in future. Upcoming patches will introduce other AVTP payloader elements that will have some common code. For that reason, this patch introduces the GstAvtpBasePayload abstract class that implements common payloader functionalities, and the GstAvtpAafPay class that extends the GstAvtpBasePayload class, implementing AAF-specific functionalities. The AAF payloader element is most likely to be used with the AVTP sink element (to be introduced by a later patch) but it could also be used with UDP sink element to implement AVTP over UDP as described in IEEE 1722-2016 Annex J. This element was inspired by RTP payloader elements.
2019-01-17 01:16:59 +00:00
'gstavtpaafpay.c',
'gstavtpcvfdepay.c',
'gstavtpcvfpay.c',
'gstavtpbasedepayload.c',
avtp: Introduce AAF payloader element This patch introduces the AVTP Audio Format (AAF) payloader element from the AVTP plugin. The element inputs audio raw data and outputs AVTP packets (aka AVTPDUs), implementing a typical protocol payloader element from GStreamer. AAF is one of the available formats to transport audio data in an AVTP system. AAF is specified in IEEE 1722-2016 section 7 and provides two encapsulation mode: PCM and AES3. This patch implements PCM encapsulation mode only. The AAF payloader working mechanism consists of building the AAF header, prepending it to the GstBuffer received on the sink pad, and pushing the buffer downstream. Payloader parameters such as stream ID, maximum transit time, time uncertainty, and timestamping mode are passed via element properties. AAF doesn't support all possible sample format and sampling rate values so the sink pad caps template from the payloader is a subset of audio/x-raw. Additionally, this patch implements only "normal" timestamping mode from AAF. "Sparse" mode should be implemented in future. Upcoming patches will introduce other AVTP payloader elements that will have some common code. For that reason, this patch introduces the GstAvtpBasePayload abstract class that implements common payloader functionalities, and the GstAvtpAafPay class that extends the GstAvtpBasePayload class, implementing AAF-specific functionalities. The AAF payloader element is most likely to be used with the AVTP sink element (to be introduced by a later patch) but it could also be used with UDP sink element to implement AVTP over UDP as described in IEEE 1722-2016 Annex J. This element was inspired by RTP payloader elements.
2019-01-17 01:16:59 +00:00
'gstavtpbasepayload.c',
'gstavtpsink.c',
'gstavtpsrc.c',
avtp: Introduce the CRF Sync Element This commit introduces the AVTP Clock Reference Format (CRF) Synchronizer element. This element implements the AVTP CRF Listener as described in IEEE 1722-2016 Section 10. CRF is useful in synchronizing events within different systems by distributing a common clock. This is useful in a scenario where there are multiple talkers who are sending data to a single listener which is processing that data. E.g. CCTV cameras on a network sending AVTP video streams to a base station to display on the same screen. It is assumed that all the systems are already time-synchronized with each other. So, the AVTP Talker essentially adjusts the AVTP Presentation Time so it's phase-locked with the reference clock provided by the CRF stream. There are 2 different roles of systems which participate in CRF data exchange. A system can either be a CRF Talker, which samples it's own clock and generates a stream of timestamps to transmit over the network, or a CRF Listener, the system which receives the generated timestamps and recovers the media clock from the timestamps. It then adjusts it's own clock to align with recovered media clock. The timestamps generated by the talker may not be continuous and the listener might have to interpolate some timestamps to recover the media clock. The number of timestamps to interpolate is mentioned in the CRF stream AVTPDU (Refer IEEE 1722-2016 Section 10.4 for AVTPDU structure). Only CRF Listener has been implemented in this commit. The CRF Sync element will create a separate thread to listen for the CRF stream. This thread will calculate and store the average period of the recovered media clock. The pipeline thread will use this stored period along with the first timestamp of the latest CRF AVTPDU received to calculate adjustment for timestamps in the audio/video streams. In case of CRF AVTPDUs with single timestamp, two consecutive CRF AVTPDUs will be used to figure out the average period of the recovered media clock. In case of H264 streams, both AVTP timestamp and H264 timestamp will be adjusted. In the future commits, another "CRF Checker" element will be introduced which will validate the timestamps on the AVTP Listener side. Which is why a lot of code has been implemented as part of the gstcrfbase class.
2020-02-06 00:17:39 +00:00
'gstavtpcrfutil.c',
'gstavtpcrfbase.c',
'gstavtpcrfsync.c',
'gstavtpcrfcheck.c',
]
avtp_dep = dependency('avtp', required: get_option('avtp'))
avtpsink: Implement synchronization mechanism The avtpsink element is expected to transmit AVTPDUs at specific times, according to GstBuffer timestamps. Currently, the transmission time is controlled in software via the rendering synchronization mechanism provided by GstBaseSink class. However, that mechanism may not cope with some AVB use-cases such as Class A streams, where AVTPDUs are expected to be transmitted at every 125 us. Thus, this patch introduces avtpsink own mechanism which leverages the socket transmission scheduling infrastructure introduced in Linux kernel 4.19. When supported by the NIC, the transmission scheduling is offloaded to the hardware, improving transmission time accuracy considerably. To illustrate that, a before-after experiment was carried out. The experimental setup consisted in 2 PCs with Intel i210 card connected back-to-back running an up-to-date Archlinux with kernel 5.3.1. In one host gst-launch-1.0 was used to generate a 2-minute Class A stream while the other host captured the packets. The metric under evaluation is the transmission interval and it is measured by checking the 'time_delta' information from ethernet frames captured at the receiving side. The table below shows the outcome for a 48 kHz, 16-bit sample, stereo audio stream. The unit is nanoseconds. | Mean | Stdev | Min | Max | Range | -------+--------+---------+---------+---------+---------+ Before | 125000 │ 2401 │ 110056 │ 288432 │ 178376 | After | 125000 │ 18 │ 124943 │ 125055 │ 112 | Before this patch, the transmission interval mean is equal to the optimal value (Class A stream -> 125 us interval), and it is kept the same after the patch. The dispersion measurements, however, had improved considerably, meaning the system is now consistently transmitting AVTPDUs at the correct time. Finally, the socket transmission scheduling infrastructure requires the system clock to be synchronized with PTP clock so this patches modifies the AVTP plugin documentation to cover how to achieve that.
2019-10-04 18:39:10 +00:00
if avtp_dep.found() and cc.has_type('struct sock_txtime', prefix : '#include <linux/net_tstamp.h>')
gstavtp = library('gstavtp',
avtp_sources,
c_args : gst_plugins_bad_args,
include_directories : [configinc],
avtp: Introduce the CRF Sync Element This commit introduces the AVTP Clock Reference Format (CRF) Synchronizer element. This element implements the AVTP CRF Listener as described in IEEE 1722-2016 Section 10. CRF is useful in synchronizing events within different systems by distributing a common clock. This is useful in a scenario where there are multiple talkers who are sending data to a single listener which is processing that data. E.g. CCTV cameras on a network sending AVTP video streams to a base station to display on the same screen. It is assumed that all the systems are already time-synchronized with each other. So, the AVTP Talker essentially adjusts the AVTP Presentation Time so it's phase-locked with the reference clock provided by the CRF stream. There are 2 different roles of systems which participate in CRF data exchange. A system can either be a CRF Talker, which samples it's own clock and generates a stream of timestamps to transmit over the network, or a CRF Listener, the system which receives the generated timestamps and recovers the media clock from the timestamps. It then adjusts it's own clock to align with recovered media clock. The timestamps generated by the talker may not be continuous and the listener might have to interpolate some timestamps to recover the media clock. The number of timestamps to interpolate is mentioned in the CRF stream AVTPDU (Refer IEEE 1722-2016 Section 10.4 for AVTPDU structure). Only CRF Listener has been implemented in this commit. The CRF Sync element will create a separate thread to listen for the CRF stream. This thread will calculate and store the average period of the recovered media clock. The pipeline thread will use this stored period along with the first timestamp of the latest CRF AVTPDU received to calculate adjustment for timestamps in the audio/video streams. In case of CRF AVTPDUs with single timestamp, two consecutive CRF AVTPDUs will be used to figure out the average period of the recovered media clock. In case of H264 streams, both AVTP timestamp and H264 timestamp will be adjusted. In the future commits, another "CRF Checker" element will be introduced which will validate the timestamps on the AVTP Listener side. Which is why a lot of code has been implemented as part of the gstcrfbase class.
2020-02-06 00:17:39 +00:00
dependencies : [gstaudio_dep, gstvideo_dep, avtp_dep, libm],
install : true,
install_dir : plugins_install_dir,
)
pkgconfig.generate(gstavtp, install_dir : plugins_pkgconfig_install_dir)
2019-04-17 00:32:46 +00:00
plugins += [gstavtp]
endif