我正在尝试在 Mac OSX 10.12.2 上捕获屏幕和音频。我更喜欢 webm 格式，因为它可以轻松分割和流式传输。此外，CPU 使用率也不错。但在这个阶段，似乎没有什么对我有用。我接受以 mp4/h265/aac 录制。
经过长达 10 个小时的尝试并多次碰壁后，我得到了以下结果：
vp8/vorbis：没有声音且视频播放太快
ffmpeg -y -f avfoundation -capture_cursor 1 -framerate 25 -r 25 -i 1:0 -vsync 2 -c:v libvpx -c:a libvorbis -b:v 1M -b:a 128K capture.webm
输出：
ffmpeg version 3.2.2 Copyright (c) 2000-2016 the FFmpeg developers
built with Apple LLVM version 8.0.0 (clang-800.0.42.1)
configuration: --prefix=/usr/local/Cellar/ffmpeg/3.2.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-opencl --disable-lzma --enable-nonfree --enable-vda
libavutil 55. 34.100 / 55. 34.100
libavcodec 57. 64.101 / 57. 64.101
libavformat 57. 56.100 / 57. 56.100
libavdevice 57. 1.100 / 57. 1.100
libavfilter 6. 65.100 / 6. 65.100
libavresample 3. 1. 0 / 3. 1. 0
libswscale 4. 2.100 / 4. 2.100
libswresample 2. 3.100 / 2. 3.100
libpostproc 54. 1.100 / 54. 1.100
[avfoundation @ 0x7fc5c2000000] Selected pixel format (yuv420p) is not supported by the input device.
[avfoundation @ 0x7fc5c2000000] Supported pixel formats:
[avfoundation @ 0x7fc5c2000000] uyvy422
[avfoundation @ 0x7fc5c2000000] yuyv422
[avfoundation @ 0x7fc5c2000000] nv12
[avfoundation @ 0x7fc5c2000000] 0rgb
[avfoundation @ 0x7fc5c2000000] bgr0
[avfoundation @ 0x7fc5c2000000] Overriding selected pixel format to use uyvy422 instead.
[avfoundation @ 0x7fc5c2000000] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, avfoundation, from '1:0':
Duration: N/A, start: 25068.515833, bitrate: 2822 kb/s
Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 2560x1600, 1000k tbr, 1000k tbn, 1000k tbc
Stream #0:1: Audio: pcm_f32le, 44100 Hz, stereo, flt, 2822 kb/s
[libvpx @ 0x7fc5c2842e00] v1.6.0
Output #0, webm, to 'capture.webm':
Metadata:
encoder : Lavf57.56.100
Stream #0:0: Video: vp8 (libvpx), yuv420p, 2560x1600, q=-1--1, 1000 kb/s, 25 fps, 1k tbn, 25 tbc
Metadata:
encoder : Lavc57.64.101 libvpx
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream #0:1: Audio: vorbis (libvorbis), 44100 Hz, stereo, fltp, 128 kb/s
Metadata:
encoder : Lavc57.64.101 libvorbis
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> vp8 (libvpx))
Stream #0:1 -> #0:1 (pcm_f32le (native) -> vorbis (libvorbis))
Press [q] to stop, [?] for help
frame= 10 fps=0.8 q=0.0 Lsize= 240kB time=00:00:00.36 bitrate=5456.9kbits/s speed=0.0284x
video:236kB audio:0kB subtitle:0kB other streams:0kB global headers:4kB muxing overhead: 2.017218%
vp9/opus：没有声音，视频播放速度太快，有时 ffmpeg 会挂起，无法退出
ffmpeg -y -f avfoundation -capture_cursor 1 -framerate 30 -r 30 -i 1:0 -c:v libvpx-vp9 -c:a libopus -crf 10 -b:v 1M -b:a 128K capture.webm
没有输出，使用ctrl+硬退出c。
mp4：音频质量差，卡顿，而且 CPU 占用也太大
ffmpeg -y -f avfoundation -capture_cursor 1 -video_size 720x480 -framerate 25 -i 1:0 -vsync 2 -preset slow -crf 22 -c:v libx264 -c:a aac -b:v 1M -b:a 128K capture.mp4
输出：
ffmpeg version N-82977-g8fd3e02-tessus Copyright (c) 2000-2016 the FFmpeg developers
built with Apple LLVM version 8.0.0 (clang-800.0.42.1)
configuration: --cc=/usr/bin/clang --prefix=/opt/ffmpeg --extra-version=tessus --enable-avisynth --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzmq --enable-version3 --disable-ffplay --disable-indev=qtkit --disable-indev=x11grab_xcb
libavutil 55. 43.100 / 55. 43.100
libavcodec 57. 70.100 / 57. 70.100
libavformat 57. 61.100 / 57. 61.100
libavdevice 57. 2.100 / 57. 2.100
libavfilter 6. 68.100 / 6. 68.100
libswscale 4. 3.101 / 4. 3.101
libswresample 2. 4.100 / 2. 4.100
libpostproc 54. 2.100 / 54. 2.100
[avfoundation @ 0x7ff6c9800000] Selected pixel format (yuv420p) is not supported by the input device.
[avfoundation @ 0x7ff6c9800000] Supported pixel formats:
[avfoundation @ 0x7ff6c9800000] uyvy422
[avfoundation @ 0x7ff6c9800000] yuyv422
[avfoundation @ 0x7ff6c9800000] nv12
[avfoundation @ 0x7ff6c9800000] 0rgb
[avfoundation @ 0x7ff6c9800000] bgr0
[avfoundation @ 0x7ff6c9800000] Overriding selected pixel format to use uyvy422 instead.
[avfoundation @ 0x7ff6c9800000] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, avfoundation, from '1:0':
Duration: N/A, start: 27439.487000, bitrate: 2822 kb/s
Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 2560x1600, 1000k tbr, 1000k tbn, 1000k tbc
Stream #0:1: Audio: pcm_f32le, 44100 Hz, stereo, flt, 2822 kb/s
No pixel format specified, yuv422p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0x7ff6c9839600] MB rate (16000000000) > level limit (2073600)
[libx264 @ 0x7ff6c9839600] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x7ff6c9839600] profile High 4:2:2, level 5.2, 4:2:2 8-bit
[libx264 @ 0x7ff6c9839600] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=1 ref=5 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=8 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=2 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=3 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=50 rc=crf mbtree=1 crf=22.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'capture.mp4':
Metadata:
encoder : Lavf57.61.100
Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv422p, 2560x1600, q=-1--1, 1000 kb/s, 1000k fps, 1000k tbn, 1000k tbc
Metadata:
encoder : Lavc57.70.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/1000000 buffer size: 0 vbv_delay: -1
Stream #0:1: Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, stereo, fltp, 128 kb/s
Metadata:
encoder : Lavc57.70.100 aac
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Stream #0:1 -> #0:1 (pcm_f32le (native) -> aac (native))
Press [q] to stop, [?] for help
frame= 158 fps= 13 q=-1.0 Lsize= 1244kB time=00:00:09.66 bitrate=1054.7kbits/s speed=0.796x
video:1200kB audio:39kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.466263%
[libx264 @ 0x7ff6c9839600] frame I:1 Avg QP:18.97 size:338028
[libx264 @ 0x7ff6c9839600] frame P:49 Avg QP:20.98 size: 15709
[libx264 @ 0x7ff6c9839600] frame B:108 Avg QP:25.01 size: 1112
[libx264 @ 0x7ff6c9839600] consecutive B-frames: 5.1% 8.9% 7.6% 78.5%
[libx264 @ 0x7ff6c9839600] mb I I16..4: 21.7% 41.3% 37.0%
[libx264 @ 0x7ff6c9839600] mb P I16..4: 0.4% 0.3% 0.6% P16..4: 4.8% 0.6% 0.7% 0.0% 0.0% skip:92.6%
[libx264 @ 0x7ff6c9839600] mb B I16..4: 0.1% 0.1% 0.0% B16..8: 2.9% 0.2% 0.1% direct: 0.0% skip:96.7% L0:49.7% L1:49.5% BI: 0.8%
[libx264 @ 0x7ff6c9839600] 8x8 transform intra:35.8% inter:23.9%
[libx264 @ 0x7ff6c9839600] direct mvs spatial:96.3% temporal:3.7%
[libx264 @ 0x7ff6c9839600] coded y,uvDC,uvAC intra: 30.5% 38.8% 34.6% inter: 0.3% 1.3% 0.4%
[libx264 @ 0x7ff6c9839600] i16 v,h,dc,p: 53% 43% 3% 1%
[libx264 @ 0x7ff6c9839600] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 57% 5% 33% 1% 1% 1% 1% 1% 2%
[libx264 @ 0x7ff6c9839600] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 35% 19% 14% 4% 5% 5% 4% 6% 7%
[libx264 @ 0x7ff6c9839600] i8c dc,h,v,p: 65% 14% 17% 3%
[libx264 @ 0x7ff6c9839600] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7ff6c9839600] ref P L0: 70.4% 2.2% 17.0% 6.3% 3.5% 0.7%
[libx264 @ 0x7ff6c9839600] ref B L0: 65.0% 22.6% 7.2% 5.1%
[libx264 @ 0x7ff6c9839600] ref B L1: 90.2% 9.8%
[libx264 @ 0x7ff6c9839600] kb/s:1014.78
[aac @ 0x7ff6ca809e00] Qavg: 581.188
Exiting normally, received signal 15.
我想知道我是否遗漏了任何可以使视频可播放的重要选项，或者这是否是 ffmpeg 中的一个错误。
答案1
您的问题似乎是计算受限的，即耗尽了对所请求的格式进行编码的 CPU 周期。
一个可行的解决方案是在主机 Mac OSX 机器上捕获流，然后将其传输到速度更快的机器上进行编码网猫。
因此，在捕获机器上，您可以运行：
ffmpeg -y -f avfoundation -capture_cursor 1 -video_size 720x480 -framerate 25 -i 1:0 -vsync 2 -c:v copy -c:a copy -f mpegts - | nc -l -p 9000
该过程将通过 netcat 将 MPEG TS 流传送到端口 9000。
现在，在编码机上，通过 netcat 接收 mpeg ts 视频流，通过 unix 管道将其提供给 ffmpeg，然后您可以调整以下示例：
（a）。对于 VAAPI，在支持的硬件上，转码为 H.264，缩放到请求的分辨率：
nc <host-ip> 9000 | ffmpeg -i pipe:0 -vaapi_device /dev/dri/renderD129 -vf 'format=nv12,hwupload,scale_vaapi=w=720:h=480' -c:v h264_vaapi -qp:v 19 -b:v 1M -bf:v 4 -threads 4 -aspect 16:9 -c:a aac -b:a 128k -f mp4 -y "capture.mp4"
对于功能更强大的工作站上可用的任何其他编码器，请根据需要对其进行调整。
问候，
Brainiarc7