June 2010 - ffmpeg-user - lists.ffmpeg.org

compil ffmpeg with alsa support
by khenyh＠gmail.com 26 Aug '12

26 Aug '12

Hi, I need your help to configure ffmpeg so as to use alsa. I have downloaded version 0.5 of ffmpeg. But I can't find how to enable alsa. I have tried "configure --enable-muxer=alsa --enable-demuxer=alsa". Then I looked at config.h and I can see "#define ENABLE_ALSA_MUXER 0", "#define ENABLE_ALSA_MUXER 0". Is there something I have missed ? Nicolas Krieger

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FFMpeg native aac decoder
by vubrhar＠gmail.com 24 Jun '12

24 Jun '12

Hi I am having some difficulty decoding audio from an IP camera, the RTSP negotiation for audio is such: v=0 o=- 1266870982069588 1266870982069588 IN IP4 10.11.11.189 s=Media Presentation e=NONE c=IN IP4 0.0.0.0 b=AS:50016 t=0 0 a=control:* a=range:npt=0.000000- m=video 0 RTP/AVP 96 b=AS:50000 a=framerate:10.0 a=control:trackID=1 a=rtpmap:96 H264/90000 a=fmtp:96 packetization-mode=1; profile-level-id=420029; sprop-parameter-sets=Z0IAKeKQFAe2AtwEBAaQeJEV,aM48gA== m=audio 0 RTP/AVP 97 b=AS:16 a=control:trackID=2 a=rtpmap:97 mpeg4-generic/16000/1 a=fmtp:97 profile-level-id=15; mode=AAC-hbr;config=1408; SizeLength=13; IndexLength=3;IndexDeltaLength=3; Profile=1; bitrate=16000; in a previous discussion, it has been pointed out that config=1408 corresponds to Low Complexity Sampling Frequency, 16000 Hz, 1 channel So this should be supported by the native aac decoder. I also was unable to transcode the following aac file to vorbis ogg http://www.nch.com.au/acm/sample.aac I am using SVN-r19905

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named pipes - > x264
by joshjdevl＠gmail.com 29 May '12

29 May '12

Hi, I was following these instructions to do a named pipe to x264 http://ffmpeg.x264.googlepages.com/piping mkfifo fifo.y4m ffmpeg -i test.mp4 -an -f yuv4mpegpipe - > fifo.y4m & x264 --quiet --crf 18 -o video.264 fifo.y4m For some reason, ffmpeg just sits here Stream mapping: Stream #0.1 -> #0.0 Press [q] to stop encoding It doesn't do any processing of test.mp4 and basically sits as a blank console. If I do something like ffmpeg -i test.mp4 -an -f yuv4mpegpipe - > test.y4m & Where test.y4m is not a named pipe, then test.y4m will end up being the yuv4 data... So I guess my question is, is there some extra option I need to compile ffmpeg or x264 with? Or is there another option I need to pass in? I tested this on Ubuntu 8.04 and centos 5.2 Thanks, Josh

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.m4a to .flv - image/video fails
by nreddig＠ptd.net 31 Mar '12

31 Mar '12

Hi all, I have greatly appreciated the information I have already gleaned from reading this forum. However I still can not solve my current problem. I am trying to convert from .m4a to .flv. These are podcast files (.m4a) built in garage band. Pictures were added as well and we would like to use this format to create weekly announcements because Garage Band is so easy for our non-technically oriented staff. Using ffmpeg the audio converts just fine but the "video" is not right. I guess it's because these files include chapter data not actual video. However when I convert it to any format the images fly through at different rates, then it seems to get stuck on a picture in the middle. The format I would like to convert to is flash so that I can easy display multiple announcement files using a flash player. I can convert .mov to .flv no problem. Converting .m4a to .mov and then .flv doesn't produce any better results. Here are the before and after files: http://www.warwicksd.org/warwick.m4a http://www.warwicksd.org/output.flv I used the following to get my conversion: ffmpeg -i warwick.m4a -b 300k -r 12 -s 300x300 -ar 22050 -y -ab 96k output.flv FFmpeg version SVN-rUNKNOWN, Copyright (c) 2000-2007 Fabrice Bellard, et al. configuration: --enable-gpl --enable-libfaac --enable-libfaad --enable- libmp3lame --disable-vhook --enable-shared libavutil version: 49.5.0 libavcodec version: 51.44.0 libavformat version: 51.14.0 built on Oct 22 2007 15:31:25, gcc: 3.3 20030304 (Apple Computer, Inc. build 1640) Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'warwick.m4a': Duration: 00:00:55.9, start: 0.000000, bitrate: 100 kb/s Stream #0.0(eng): Audio: mpeg4aac, 44100 Hz, stereo Stream #0.1(eng): Video: mjpeg, yuvj420p, 300x300, 44100.00 fps(r) Stream #0.2(eng): Data: tx3g / 0x67337874 Stream #0.3(eng): Data: text / 0x74786574 Output #0, flv, to 'output.flv': Stream #0.0(eng): Video: flv, yuv420p, 300x300, q=2-31, 300 kb/s, 12.00 fps (c) Stream #0.1(eng): Audio: libmp3lame, 22050 Hz, stereo, 96 kb/s Stream mapping: Stream #0.1 -> #0.0 Stream #0.0 -> #0.1 Press [q] to stop encoding frame= 83 fps= 21 q=2.0 Lsize= 1099kB time=6.9 bitrate=1301.6kbits/s video:70kB audio:657kB global headers:0kB muxing overhead 51.296550% .mov files convert nicely to .flv but these .m4as are just not working. Our current staff is very eager to use these Garage Band files to communicate announcements. I have been so desperate to get this particular file type to convert that I have been experimenting with grabbing the frames every 5 secs. and then rebuilding the images into video. This produces strange results and seems to be more programming then should be necessary. Thanks in advanced for any solutions you can provide. Nancy Reddig Web Programmer Warwick SD

4 3

Scene detection
by foripepe＠yahoo.com 01 Mar '12

01 Mar '12

Hi, I would like to generate images from videos at every scene changes. My present solution is: - ffmpeg -i source_video -r 25 -an -vcodec mjpeg destination_video.avi - lav2yuv -S list.el destination_video.avi It generates a scene list text file with time codes that I use later to creating images. I was wondering maybe there is an easier solution. I have browsed the net to get a better solution (ffmpeg, sc_threshold etc.), but I couldn't find any other just my present lav2yus solution. Is it possible to use ffmpeg to create images on scene changes? Or is it possible to use ffmpeg to create a text file with the time codes of scene changes? If you have any idea, I would be very happy. Thanks in advance.

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Can ffmpeg extract clips from ogg video files?
by vfclists＠googlemail.com 23 Jan '12

23 Jan '12

I am trying to extract clips from an ogg video generated from vlc 1.0 and ffmpeg always crashes when trying to do so. Is ffmpeg capable of doing that? -- Frank Church ======================= <a href="http://devblog.brahmancreations.com">devblog.brahmancreations.com</a>

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Frame/gop accurate video splitting (fps, gop, length known)
by abodera＠gmail.com 22 Dec '11

22 Dec '11

Hey there! A simple use case: 1) a sample mp4 file of 23.98 tbr, 264 + aac, 1:51.27 in length 2) the file (lotr trailer) encoded with: ./ffmpeg -i ./lordoftherings_h640_ml.mov -vcodec libx264 -g 50 ./lord.mp4 3) we want to split it in 3 parts: 30s, 10s and the rest of the stream Chunks we want to have: 1) ~30s (00:00:00 - 00:00:30) 2) ~10s (00:00:30 - 00:00:40) 3) ~71s (00:00:40 - 00:01:51) File info: Duration: 00:01:51.27, start: 0.000000, bitrate: 256 kb/s Stream #0.0(eng): Video: h264, yuv420p, 640x272, 192 kb/s, 47.90 fps, 23.98 tbr, 24k tbn, 47.95 tbc Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16, 58 kb/s The only tools right now are -vframes, -ss and -t. Frame-accurate seeking is missing/broken (?). Below is my approach. a) chunk 1 is 30s, so with 23.98 fps that gives 719.5 frames. b) Because it's gop 50 we round down to 700 frames = 29.1909925 seconds from start c) Chunk 1 extraction: "-vframes 699" d) Chunk 2 starts from frames 700 and ends in 10s = 239.8 frames ~ 250 frames (gop 50) e) Chunk 2 extraction: "-ss 29.1909925 -vframes 250" f) Chunk 3 starts at 40s = 959.2th frames (23.98 fps). Rounding down to 50 gives us 950th frame g) 950th frame is at aproximately 39.61635 sec. g) Chunk 3 extraction: "-ss 39.61635" Of course I wouldn't be bothering the community if it worked properly :-) The chunks are off by many seconds, lengths are off. Please assist - what am I doing wrong? Is there any more elegant way to do that? Also: a simpler case that I thought would "just work" - split the stream in two: ./ffmpeg -y -ss -t 30 -i ./lord.mp4 -vcodec copy -acodec copy lord-chunk1.mp4 ./ffmpeg -y -ss 00:00:30 -i ./lord.mp4 -vcodec copy -acodec copy lord-chunk2.mp4 It doesn't work! This will also end badly with two arbitrary length chunks with seek times that make little sense. How is it done properly? Thanks! Arthur. ps: FFmpeg version SVN-r20880 -- __ /.)\ +48 695 600 936 \(./ abodera at gmail.com

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iPhone Matrix Rotation Info
by ben.knight＠f-i.com 27 Sep '11

27 Sep '11

Hi. I am using ffmpeg to encode videos both uploaded from the web and from iPhones. Currently, we are rotating the iPhone videos with another script. This has worked great so far however we just launched a mobile version of our site and now videos that have been rotated 90 degrees won?t play on the iPhone. The videos that are rotated 270 degrees work fine. I am wondering if there is a way to encode the file with ffmpeg so that it keeps the rotation matrix information from the iPhone so that if I try to play it again on the iPhone it works? Thanks *Ben*

6 11

milliseconds to mpeg-ts pts/dts
by steuer＠unixsystems.de 07 Sep '11

07 Sep '11

guys, i try to create an mpegts file from H.264 and ACC raw frames that i receive from a network connection. I create AVPacket structures, set data, size, pts and dts etc. manually. For the stream that I receive, PTS and DTS seem to be equal, so I just calculate the packet pts and dts with incoming pts / 1000.0 * 90000.0 I do that for audio and video. Unfortunately that seems to be wrong as ffmpeg states "dts < pcr, TS is invalid" after a couple of seconds. I seems that the timestamps run out of sync with the internal pcr reference clock. What would be the correct way to calculate the pts and dts of the mpegts stream? Thanks alot for your help! Cheers, Heri

3 2

Hint tracks support for MP4
by stas.oskin＠gmail.com 16 Aug '11

16 Aug '11

Hi. Any idea if FFMPEG supports / will be supporting adding hint tracks to MP4 files for RTSP streaming? Regards.

3 2