April 2015 - ffmpeg-user - lists.ffmpeg.org

Recording audio from mic and speakers from commandline
by Mohan G 28 Sep '21

28 Sep '21

Hi, I am using ffmpeg version 2.4.7 on Fedora-21 workstation. I want to record audio, simultaneously from mic and speakers as separate streams. I am using the following command for it. ffmpeg -f alsa -i pulse -f alsa -i default -acodec libmp3lame -map 0:0 -map 1:0 outfile.mkv But after executing this command in terminal, I have to goto "Volume Control" settings in GUI, then goto "Recording" tab, change the "capture from" of one channel to "Built-in Audio Analog Stereo" (i.e., Mic) and the "capture from" of another channel to "Monitor of Built-in Audio Analog Stereo" (i.e., Speakers). But how can this be done completely from command-line, for automating it to use in scripts. - Mohan

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Failed to resolve hostname: Ubuntu static builds
by hdn8 03 Mar '18

03 Mar '18

Using the binaries from http://johnvansickle.com/ I get an error when using a http input, "failed to resolve hostname": (using ffprobe, but also with ffmpeg): ffprobe version N-41351-g676110e- http://johnvansickle.com/ffmpeg/ Copyright (c) 2007-2014 the FFmpeg developers built on Oct 15 2014 01:22:19 with gcc 4.8 (Debian 4.8.3-11) configuration: --enable-gpl --enable-version3 --disable-shared --disable-debug --enable-runtime-cpudetect --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --disable-ffserver --enable-libass --enable-gnutls --cc=gcc-4.8 libavutil 54. 10.100 / 54. 10.100 libavcodec 56. 5.100 / 56. 5.100 libavformat 56. 9.100 / 56. 9.100 libavdevice 56. 1.100 / 56. 1.100 libavfilter 5. 1.106 / 5. 1.106 libswscale 3. 1.101 / 3. 1.101 libswresample 1. 1.100 / 1. 1.100 libpostproc 53. 3.100 / 53. 3.100 [tcp @ 0x3f82100] Failed to resolve hostname mirrorblender.top-ix.org: Name or service not known http://mirrorblender.top-ix.org/peach/bigbuckbunny_movies/big_buck_bunny_48…: Input/output error Note I have tried with various http sources/hosts, all same result. Using the builds from ffmpeg.gusari.org it works fine: ffprobe version N-63893-gc69defd Copyright (c) 2007-2014 the FFmpeg developers built on Jul 16 2014 05:38:01 with gcc 4.6 (Debian 4.6.3-1) configuration: --prefix=/root/ffmpeg-static/64bit --extra-cflags='-I/root/ffmpeg-static/64bit/include -static' --extra-ldflags='-L/root/ffmpeg-static/64bit/lib -static' --extra-libs='-lxml2 -lexpat -lfreetype' --enable-static --disable-shared --disable-ffserver --disable-doc --enable-bzlib --enable-zlib --enable-postproc --enable-runtime-cpudetect --enable-libx264 --enable-gpl --enable-libtheora --enable-libvorbis --enable-libmp3lame --enable-gray --enable-libass --enable-libfreetype --enable-libopenjpeg --enable-libspeex --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-version3 --enable-libvpx libavutil 52. 89.100 / 52. 89.100 libavcodec 55. 66.101 / 55. 66.101 libavformat 55. 43.100 / 55. 43.100 libavdevice 55. 13.101 / 55. 13.101 libavfilter 4. 8.100 / 4. 8.100 libswscale 2. 6.100 / 2. 6.100 libswresample 0. 19.100 / 0. 19.100 libpostproc 52. 3.100 / 52. 3.100 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'http://mirrorblender.top-ix.org/peach/bigbuckbunny_movies/big_buck_bunny_48…': Metadata: major_brand : qt minor_version : 537199360 compatible_brands: qt creation_time : 2008-05-27 18:32:32 timecode : 00:00:00:00 Duration: 00:09:56.46, start: 0.000000, bitrate: 3342 kb/s Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 854x480, 2899 kb/s, 24 fps, 24 tbr, 2400 tbn, 4800 tbc (default) Metadata: creation_time : 2008-05-27 18:32:32 handler_name : Apple Alias Data Handler encoder : H.264 Stream #0:1(eng): Data: none (tmcd / 0x64636D74) (default) Metadata: creation_time : 2008-05-27 18:32:32 handler_name : Apple Alias Data Handler timecode : 00:00:00:00 Stream #0:2(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 437 kb/s (default) Metadata: creation_time : 2008-05-27 18:32:32 handler_name : Apple Alias Data Handler The error from http://johnvansickle.com/ffmpeg/ is the same for the nightly and version 2.4. The gusari.org binaries havent been built since July 16, for now I am using ffprobe from gusari for http sources and for file sources johnvansickle. From where are you getting your (supposedly stable) binaries? Ubuntu x86_64 GNU/Linux -- View this message in context: http://ffmpeg-users.933282.n4.nabble.com/Failed-to-resolve-hostname-Ubuntu-… Sent from the FFmpeg-users mailing list archive at Nabble.com.

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Adding user-defined SEI messages thru libavcodec/libx264
by SF 06 Jan '18

06 Jan '18

Hi, I am searching a way to insert private SEI messages before each picture when encoding with x264. As far as i see from the libx264.c code, it is not supported up to now. Am i correct ? If yes, i am willing to push patch to support this, but do you have a preferred way to do this (ie thru medata field of AVFrame ? thru sidedata of AVFrame ? ...) Thanks for your hints, Regards, SF

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Syncing clips based on audio waveform?
by Arthur Wait 05 Oct '17

05 Oct '17

Hi all, This is coming from out of left field I imagine, but I'm wondering if anyone knows of a filter (or chain of filters) which would allow me to align/sync two video clips based on matches in their audio waveforms. I'm shooting events with multiple cameras and would like to either trim the clips to a precise, matching starting frame or generate a metadata "offset" marker indicating how far off one clip is from the other in time. Then I can trim the clips to match. Is this possible in ffmpeg (or anywhere else for that matter!)? Thanks very much! Art

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could not find codec parameters for stream 0 unspecified size
by Ashish Lal 09 Aug '17

09 Aug '17

I am trying to convert a live rtsp stream (H264 + MPEG2 TS ) into MP4 using ffmpeg. I am getting an error "could not find codec parameters for stream 0 unspecified size". Any help in fixing this is appreciated. ffmpeg -rtsp_transport tcp -i rtsp://AA.BB.CC.DD:5555/mpeg2TransportStreamFr omUDPSourceTest -analyzeduration 999999999 -probesize 99999999 -vcodec libx264 -s 176x144 -b:v 256k -f mp4 -movflags frag_keyframe+empty_moov op.mp4 ffmpeg version 2.2.2 Copyright (c) 2000-2014 the FFmpeg developers built on May 27 2014 09:12:51 with gcc 4.7 (Debian 4.7.2-5) configuration: --enable-libx264 --enable-encoder=libx264 --enable-libvpx --pre fix=/home/ashish/ffmpeg-2.2.2/mybuild --enable-gpl --enable-debug --disable-stri pping --disable-optimizations --enable-memalign-hack libavutil 52. 66.100 / 52. 66.100 libavcodec 55. 52.102 / 55. 52.102 libavformat 55. 33.100 / 55. 33.100 libavdevice 55. 10.100 / 55. 10.100 libavfilter 4. 2.100 / 4. 2.100 libswscale 2. 5.102 / 2. 5.102 libswresample 0. 18.100 / 0. 18.100 libpostproc 52. 3.100 / 52. 3.100 [NULL @ 0x235cd60] non-existing PPS 0 referenced [h264 @ 0x235cd60] non-existing PPS 0 referenced [h264 @ 0x235cd60] decode_slice_header error [h264 @ 0x235cd60] no frame! [h264 @ 0x235cd60] non-existing PPS 0 referenced ......... ......... Last message repeated 1 times [h264 @ 0x235cd60] decode_slice_header error [h264 @ 0x235cd60] no frame! [h264 @ 0x235cd60] non-existing PPS 0 referenced [rtsp @ 0x232fc40] decoding for stream 0 failed [rtsp @ 0x232fc40] Could not find codec parameters for stream 0 (Video: h264 ([2 7][0][0][0] / 0x001B)): unspecified size Consider increasing the value for the 'analyzeduration' and 'probesize' options rtsp://AA.BB.CC.DD:5555/mpeg2TransportStreamFromUDPSourceTest: could not find codec parameters Conversion failed! Regards Ashish

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Compiling FFMPEG with ffplay support
by Stas Oskin 14 Jun '17

14 Jun '17

Hi. Did the compilation parameters changed in recent FFMPEG version? Configuring the FFMPEG like this: ./configure --prefix=/usr --enable-pthreads Does not produce ffplay anymore. I tried to add --enable-ffplay, without any result. Any idea what I'm missing? Thanks.

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How do I encode DVB Subtitles?
by Wagner Patriota 02 May '17

02 May '17

*QUESTION 1:* How do I add a STR file to a MPEG-TS file with the "DVB subtitle codec"? If so, could you give me a sample command line? Thank. I am trying: ffmpeg -i video.ts *-i subtitle.srt* -vcodec copy -acodec copy *-scodec dvbsub* output.ts The stream is created because I can see it with MediaInfo, but the subtitles don't appear! *QUESTION 2:* How do I use the command *slang*? I try to use it, but ffmpeg says the command doesn't exist. Thank you.

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How to use global_header, fflags, rtpflags parameter.
by Ly Tran Cong 06 Dec '16

06 Dec '16

Hello, Can anyone tell me how to use flags +global_header, fflags +latm, rtpflags +latm Which parameter using with video encode and which parameter using with audio encode. Thanks -- Regards, Tran Ly Vega Corporation 98 Hoang Quoc Viet Str, Hanoi, Vietnam Tel: 84 4 755 4190 Fax: 84 4 755 4190 Mobile: 84 91 487 1115 www.vega.com.vn; www.clip.vn; www.chacha.vn; www.ringring.vn

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Decklink Capture
by Reuben Martin 20 Apr '16

20 Apr '16

I’ve built 2.6.0 with decklink support, but I haven’t been able to work out how to interface with it. (Even after poking around in the code) Is there info / documentation on this somewhere? Specifically I can’t figure out how to set the audio / video input types and modes. -Reuben

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Flip in sws_scale
by romulo.fernandes＠gmail.com 11 Mar '16

11 Mar '16

Hello, I'm using libswscale to scale and convert pixel format from frames that I capture from the screen. In my windows build the frames that I capture are in DIB format. I'm using FFMPEG SVN rev 16437. Calling sws_scale normally I get the image correctly, except that it's vertically flipped. If I change the srcSliceY from 0 to srcHeight and srcSliceH from srcHeight to 0, I get a grey image (with correct dimensions). If I keep the srcSliceY in 0 and change srcSliceH from srcHeight to -srcHeight, I also get that grey image. Is there a way to make sws_scale flip the image for me ?

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