March 2017 - ffmpeg-user - lists.ffmpeg.org

How to specify Audio bit depth for test sources?
by Basin Ilya 02 Mar '17

02 Mar '17

Hi. Different test sources have different bit depth: ffplay -f lavfi aevalsrc="0" # Audio: pcm_f64le ffplay -f lavfi anullsrc # Audio: pcm_u8 If I want to do some PCM math in the audio filter, I'll need to adapt the filter for each different input bit depth. There's no filter to change the depth. "aresample" only changes the sample rate. -acodec option won't do here, because it takes effect AFTER filtering and some tools don't have it (ffplay). -isf: I was unable to make it work The only workaround is to use /dev/zero as the source. Then you can specify the needed input format.

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ogg encoder always adds 128-255 extra samples
by Basin Ilya 02 Mar '17

02 Mar '17

Hi. I'm trying to create a set of chainable ogg files out of a long wav file. However, the produced ogg files are always 128-255 samples longer than the source PCM data and the extra data looks like anti-click or fade-out. See the attached image. test0 was made directly. test1 was made via an intermediate ogg file. I tried to choose a duration whose sample count is divisible by 64 or 128, but that didn't help. # produce 10 seconds of noise ffmpeg -y -t 10 -f lavfi -i aevalsrc="random(0)*2-1" -c:a pcm_s16le test.wav ( </dev/null ffmpeg -y -ss 0 -t 0.995567 -i test.wav -af "ashowinfo" test0.wav </dev/null ffmpeg -y -ss 0 -t 0.995567 -i test.wav -af "ashowinfo" test1.ogg # pts:43008 nb_samples:897 </dev/null ffmpeg -y -i "test1.ogg" -af "ashowinfo" test1.wav # pts:44032 nb_samples:128 ) _ The only workaround I see is to make a slightly longer ogg, then use "-acodec copy" and "-t" to discard 1 or 2 unneeded ogg frames.

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Video and Audio is off-sync on Decklink SDI output
by Tung Tran 02 Mar '17

02 Mar '17

Dear all I am testing to setup a decoder with ffmpeg, take live stream in (RTMP/HLS,.) and output to Decklink SDI. Its working but I have the issue of audio and video is off-sync on decklink SDI output, I tried to play around with vf setpts and af asetpts but couldnt make video/audio to sync. Any input will be very appreciated. Here is my command so far * ffmpeg -i rtmp://something -vf "setpts=PTS-STARTPTS" -af "asetpts=PTS-STARTPTS" -f decklink -pix_fmt uyvy422 "DeckLink SDI" * Video and audio of input rtmp is synced on VLC or other software. --- Best regards, *Tung Tran*

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libass : ERROR NOT in Path in ffmpeg compile
by derekg 02 Mar '17

02 Mar '17

Dear Help , Hi , I am trying to set up a fully working version of ffmpeg on my Linux Mint Qiana 17 OS , using thecomprehensive guide https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu . Please find attached a config.log complaining about a libass package not in the path . Also please see a second attached file pkg-configversion.txt showing releases data . I am an English old-age-pensioner and using Mint's Synaptic Package Manager I had Completely Removed ffmpeg version 7:2.4.3-1ubuntu1~trusty before following the guide . Any suggestions will be gratefully received and requests for more data will be acted upon . Thank you , Derek Hopley

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minimal nb_sambles in ogg frame
by Basin Ilya 02 Mar '17

02 Mar '17

Hi. I'm splitting a .wav file into a set of chainable .ogg files all having 1 second duration. I'm using input flags: "-ss n -t 1" When I concatenate these ogg files, the resulting clip is slightly longer than the original. Is it because the minimal nb_sambles in ogg frame is 128 and a set of ogg frames cannot contain exactly 44100 samples? </dev/null ffmpeg -y -ss 0 -t 1 -i test.wav -af "ashowinfo" test1.ogg # pts:44032 nb_samples:68 </dev/null ffmpeg -y -ss 1 -t 1 -i test.wav -af "ashowinfo" test2.ogg # pts:44032 nb_samples:68 </dev/null ffmpeg -y -i "concat:test1.ogg|test2.ogg" -af "ashowinfo" test5.wav # pts:88132 nb_samples:128 88132 + 128 != 88200 ffprobe test5.wav # Duration: 00:00:02.01

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Stream from a dynamic collection
by Jorge Reyero 02 Mar '17

02 Mar '17

Hi, I'm new using ffmpeg so I don't know if what I want is possible or not, I hope you can tell. I have a video collection (place in the server filesystem) which is growing every minute. I want to simulate a live stream from this video collection and if the stream reaches the end of the videos it should start form the first one again. I know how to repeat a single video and how to play videos from static video collection but I have no idea how do it with this dynamic collection. Any idea? Is it possible to do that? Thanks

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Difference in ffmpeg command execution time
by Vivek Jain 01 Mar '17

01 Mar '17

Hi, On trying to create video using ffmpeg as per command below, it takes much more time (around 6 minutes) on AWS lambda and EC2 instances where as it takes just 2 minutes on my local mac. I understand run time differs on CPU, but I am not able to figure out what needs to be done in order to get it run within 5 minutes on lambda. Or it could be due to differences in or missing libraries. Could someone please point me in right direction? Command: ffmpeg -safe 0 -f concat -i /tmp/config.txt -i /tmp/audio.mp3 -y -pix_fmt yuv444p -shortest /tmp/out_ffff.mp4 Attached are the logs of both the machines. -- Thanks, Vivek

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CodecPrivateData is empty when h264_vaapi encoder used
by w_boba 01 Mar '17

01 Mar '17

I am trying to use new CPU with VA-API enabled h264 encoder on FFmpeg (ffmpeg version n3.2.4-4-g36fff6c). I have no issues encoding "offline" files with h264_vaapi encoder, but when I try to encode live streams and push output to SmoothStream server (using ISMV muxer) new streams do not work. Exactly same configuration works fine with libx264 encoder. So far I figured that after libx264 encoder ffmpeg correctly sets "CodecPrivateData" field data but h264_vaapi sends empty data field. Old command line (works fine): ffmpeg -y -i "udp://235.1.1.136:392" -g 30 -r ntsc -movflags isml+frag_keyframe -sc_threshold 0 -c:v libx264 -c:a aac -ac 2 -b:a 128k -b:v 3072k -f ismv "http://10.100.1.14/testenc1.isml/Streams(testenc1)" New command line (encoding works, but streams do not play): ffmpeg -y -vaapi_device /dev/dri/renderD128 -i "udp://235.1.1.136:392" -vf 'format=nv12,hwupload' -g 30 -r ntsc -movflags isml+frag_keyframe -sc_threshold 0 -c:v h264_vaapi -c:a aac -ac 2 -b:a 128k -b:v 3072k -f ismv "http://10.100.1.14/testenc1.isml/Streams(testenc1)" -- View this message in context: http://www.ffmpeg-archive.org/CodecPrivateData-is-empty-when-h264-vaapi-enc… Sent from the FFmpeg-users mailing list archive at Nabble.com.

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