I'm trying to capture a stream from a webcam, and it says "press [q] to stop, [?] for help". But neither of those keys has any effect. The only way I can get it to stop is by pressing ctrl-C repeatedly, and then it gives an error and the output file is not playable. I'm running ffmpeg in Terminal in OS X 10.10.5. The webcam is a Logitech c920. $ ffmpeg -f avfoundation -video_size 1920x1080 -framerate 30 -pixel_format uyvy422 -i "0" -vcodec libx264 -pix_fmt yuv420p test.mov ffmpeg version 3.0.git Copyright (c) 2000-2016 the FFmpeg developers built with Apple LLVM version 7.0.2 (clang-700.1.81) configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-avresample --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libsoxr --enable-libspeex --enable-libass --enable-libbluray --enable-lzma --enable-gnutls --enable-fontconfig --enable-libfreetype --enable-libfribidi --disable-indev=jack --disable-outdev=xv --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/cc --enable-vda --enable-audiotoolbox --enable-videotoolbox --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-nonfree --enable-libfdk-aac --enable-libfaac libavutil 55. 24.100 / 55. 24.100 libavcodec 57. 42.100 / 57. 42.100 libavformat 57. 36.100 / 57. 36.100 libavdevice 57. 0.101 / 57. 0.101 libavfilter 6. 45.100 / 6. 45.100 libavresample 3. 0. 0 / 3. 0. 0 libswscale 4. 1.100 / 4. 1.100 libswresample 2. 0.101 / 2. 0.101 libpostproc 54. 0.100 / 54. 0.100 [avfoundation @ 0x7f95e200da00] Stream #0: not enough frames to estimate rate; consider increasing probesize Input #0, avfoundation, from '0': Duration: N/A, start: 24544.717833, bitrate: N/A Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 1920x1080, 1000k tbr, 1000k tbn File 'test.mov' already exists. Overwrite ? [y/N] y [mov @ 0x7f95e5801600] Frame rate very high for a muxer not efficiently supporting it. Please consider specifying a lower framerate, a different muxer or -vsync 2 [libx264 @ 0x7f95e5805c00] MB rate (8160000000) > level limit (2073600) [libx264 @ 0x7f95e5805c00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 [libx264 @ 0x7f95e5805c00] profile High, level 5.2 [libx264 @ 0x7f95e5805c00] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=34 lookahead_threads=5 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=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00 [mov @ 0x7f95e5801600] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead. [mov @ 0x7f95e5801600] WARNING codec timebase is very high. If duration is too long, file may not be playable by quicktime. Specify a shorter timebase or choose different container. Output #0, mov, to 'test.mov': Metadata: encoder : Lavf57.36.100 Stream #0:0: Video: h264 (avc1 / 0x31637661), yuv420p, 1920x1080, q=2-31, 1000k fps, 1000k tbn Metadata: encoder : Lavc57.42.100 libx264 Side data: cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1 Stream mapping: Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264)) Press [q] to stop, [?] for help ^Cav_interleaved_write_frame(): Immediate exit requested ^CReceived > 3 system signals, hard exiting $