如何解决如何将 gst-element avdec_h264 设置为多线程解码
我使用 gstreamer 1.16.2，在 ubuntu20.04 之类的 os 上运行，没有硬件来加速解码。我的想法是通过优化解码的 cpu 成本来减少视频延迟。这是我接收和解码远程rtp流的管道。
200390 200356 54 20:15 ? 00:01:05 /usr/bin/gst-launch-1.0 -v udpsrc port=1991 caps="application/x-rtp,media=video" ! rtpjitterbuffer latency=20 ! rtpmp2tdepay ! tsdemux name=demuxer demuxer. ! queue name=video_ch max-size-buffers=0 max-size-time=0 ! h264parse ! queue name=dec0 ! avdec_h264 max-threads=2 skip-frame=1 ! videoconvert n-threads=4 ! xvimagesink display=:0 sync=false demuxer. ! queue name=audio_ch max-size-buffers=0 max-size-time=0 ! aacparse ! avdec_aac ! audioconvert ! audioresample ! autoaudiosink
但我发现 avdec_h264 在多线程下不起作用，我认为“最大线程”应该可以工作。见下面的“top -H”打印，所有解码工作都加载在200398线程上，命名为“dec0”。
top -H | grep dec
200398 root 20 0 1164484 69284 46408 S 57.9 0.9 0:42.92 dec0:src
200398 root 20 0 1161412 66248 43372 R 32.3 0.8 0:43.90 dec0:src
200398 root 20 0 1164484 69284 46408 S 82.6 0.9 0:46.41 dec0:src
200398 root 20 0 1161412 66248 43372 R 82.9 0.8 0:48.93 dec0:src
200398 root 20 0 1164484 69284 46408 S 59.0 0.9 0:50.73 dec0:src
200398 root 20 0 1164484 69284 46408 S 32.9 0.9 0:51.73 dec0:src
200398 root 20 0 1164484 69284 46408 S 24.4 0.9 0:52.47 dec0:src
200398 root 20 0 1164484 69284 46408 S 24.3 0.9 0:53.21 dec0:src
200398 root 20 0 1164484 69284 46408 S 24.0 0.9 0:53.94 dec0:src
这是“父PID”200390的pstree打印，它是/usr/bin/gst-launch-1.0程序。
pstree -pt 200390
gst-launch-1.0(200390)─┬─{audio_ch:src}(200399)
├─{audio_ch:src}(201471)
├─{dec0:src}(200398)
├─{dec0:src}(200405)
├─{gmain}(200404)
├─{gst-launch-1.0}(200397)
├─{rtpjitterbuffer}(200402)
├─{timer}(200401)
├─{udpsrc0:src}(200403)
├─{video_ch:src}(200400)
├─{videoconvert}(200406)
├─{videoconvert}(200407)
└─{videoconvert}(200408)
我调试线程20045，它是200398的兄弟解码线程，它似乎被阻塞了：pthread_cond_wait，因为spawned。
(gdb) bt
#0 0x0000007f83073038 in **pthread_cond_wait**@@GLIBC_2.17 () at /lib/aarch64-linux-gnu/libpthread.so.0
#1 0x0000007f800c5cbc in () at /lib/aarch64-linux-gnu/libavutil.so.56
#2 0x0000007f8306c4fc in start_thread () at /lib/aarch64-linux-gnu/libpthread.so.0
#3 0x0000007f82fc530c in () at /lib/aarch64-linux-gnu/libc.so.6
这是线程信息：
Attaching to process 200390
[New LWP 200397]
[New LWP 200398]
[New LWP 200399]
[New LWP 200400]
[New LWP 200401]
[New LWP 200402]
[New LWP 200403]
[New LWP 200404]
[New LWP 200405]
[New LWP 200406]
[New LWP 200407]
[New LWP 200408]
[New LWP 201471]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
0x0000007f82ceedb8 in poll () from /lib/aarch64-linux-gnu/libc.so.6
(gdb) info threads
Id Target Id Frame
* 1 Thread 0x7f83114790 (LWP 200390) "gst-launch-1.0" 0x0000007f82ceedb8 in poll () from /lib/aarch64-linux-gnu/libc.so.6
2 Thread 0x7f7866e1e0 (LWP 200397) "gst-launch-1.0" 0x0000007f82cc541c in clock_nanosleep () from /lib/aarch64-linux-gnu/libc.so.6
3 Thread 0x7f77e6d1e0 (LWP 200398) "dec0:src" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
4 Thread 0x7f776311e0 (LWP 200399) "audio_ch:src" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
5 Thread 0x7f76e301e0 (LWP 200400) "video_ch:src" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
6 Thread 0x7f7662f1e0 (LWP 200401) "timer" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
7 Thread 0x7f75e2e1e0 (LWP 200402) "rtpjitterbuffer" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
8 Thread 0x7f7562d1e0 (LWP 200403) "udpsrc0:src" 0x0000007f82ceedb8 in poll () from /lib/aarch64-linux-gnu/libc.so.6
9 Thread 0x7f74e2c1e0 (LWP 200404) "gmain" 0x0000007f82ceedb8 in poll () from /lib/aarch64-linux-gnu/libc.so.6
10 Thread 0x7f57fff1e0 (LWP 200405) "dec0:src" 0x0000007f82da6038 in pthread_cond_wait@@GLIBC_2.17 () from /lib/aarch64-linux-gnu/libpthread.so.0
11 Thread 0x7f574fe1e0 (LWP 200406) "videoconvert" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
12 Thread 0x7f56cfd1e0 (LWP 200407) "videoconvert" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
13 Thread 0x7f564fc1e0 (LWP 200408) "videoconvert" 0x0000007f82cf4760 in syscall () from /lib/aarch64-linux-gnu/libc.so.6
14 Thread 0x7f554031e0 (LWP 201471) "audio_ch:src" 0x0000007f82ceedb8 in poll () from /lib/aarch64-linux-gnu/libc.so.6
(gdb) c
Continuing.
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