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• very low latency streaminig with ffmpeg using a webcam

  22 mars 2017, par userDtrm

  I’m trying to configure ffmpeg to do a real-time video streaming using a webcam. The ffmpeg encoder command I use is as follows.

  ffmpeg -f v4l2 -input_format yuyv422 -s 640x480 -i /dev/video0 -c:v libx264 -profile:v baseline -trellis 0 -subq 1 -level 32 -preset superfast -tune zerolatency -me_method epzs -crf 30 -threads 0 -bufsize 1 -refs 4 -coder 0 -b_strategy 0 -bf 0 -sc_threshold 0 -x264-params vbv-maxrate=2000:slice-max-size=1500:keyint=30:min-keyint=10: -pix_fmt yuv420p -an -f mpegts udp://192.168.1.8:5001

  The ffplay command used to display the video feed is,

  ffplay -analyzeduration 1 -fflags -nobuffer -i udp://192.168.1.8:5001

  However, I’m experiencing a latency of 0.5 - 1.0s latency in the video stream. Is there a way to reduce this to a number less than 100ms. Also, when I replace the v4l2 camera capture with a screen capture using x11grab, the stream is almost real-time and I experience no noticeable delays. Moreover, changing the encoder from x264 to mpeg2 had no effect on the latency. In addition, the statistics from the ffmpeg shows that the encoder is performing at a 30fps rate, which I believe indicates that the encoding is real-time. This leaves me with only one reason for the experienced delay.

  • Is there a significant delay in buffers when using v4l2 during video capturing in a webcam ?
  • I don’t think the transmission delay is in effect in this case as I see no latencies when screen capture is used under the same conditions.
  • Can this latency be further reduced ?. Can someone think of a different encoder configuration to be used instead of the one that I’ve been using ?.

  Any suggestions or assistance is highly appreciated.

  Thank You.

• very low latency streaminig with ffmpeg using a webcam

  22 mars 2017, par userDtrm

  I’m trying to configure ffmpeg to do a real-time video streaming using a webcam. The ffmpeg encoder command I use is as follows.

  ffmpeg -f v4l2 -input_format yuyv422 -s 640x480 -i /dev/video0 -c:v libx264 -profile:v baseline -trellis 0 -subq 1 -level 32 -preset superfast -tune zerolatency -me_method epzs -crf 30 -threads 0 -bufsize 1 -refs 4 -coder 0 -b_strategy 0 -bf 0 -sc_threshold 0 -x264-params vbv-maxrate=2000:slice-max-size=1500:keyint=30:min-keyint=10: -pix_fmt yuv420p -an -f mpegts udp://192.168.1.8:5001

  The ffplay command used to display the video feed is,

  ffplay -analyzeduration 1 -fflags -nobuffer -i udp://192.168.1.8:5001

  However, I’m experiencing a latency of 0.5 - 1.0s latency in the video stream. Is there a way to reduce this to a number less than 100ms. Also, when I replace the v4l2 camera capture with a screen capture using x11grab, the stream is almost real-time and I experience no noticeable delays. Moreover, changing the encoder from x264 to mpeg2 had no effect on the latency. In addition, the statistics from the ffmpeg shows that the encoder is performing at a 30fps rate, which I believe indicates that the encoding is real-time. This leaves me with only one reason for the experienced delay.

  • Is there a significant delay in buffers when using v4l2 during video capturing in a webcam ?
  • I don’t think the transmission delay is in effect in this case as I see no latencies when screen capture is used under the same conditions.
  • Can this latency be further reduced ?. Can someone think of a different encoder configuration to be used instead of the one that I’ve been using ?.

  Any suggestions or assistance is highly appreciated.

  Thank You.

• What is the best solution to convert old videos to newer more optimised formats ? [on hold]

  9 septembre 2019, par Jack

  Not too sure if this is the wrong place - please move it as I couldn’t find a more suitable network

  I have loads of media (Movies, TV Shows) as well as home videos (old VHS stuff ripped using some awful VHS to digital kit)

  Most of the movies/TV shows are in H264 (MP4/MKV containers) format, however some older ones are in AVI and WMV - I’d like to convert these into either H264 or a newer format (HEVC ?) To save some disk space and also because WMVs and AVIs are getting harder to deal with nowadays. I’m concerned about losing quality and am wondering what would be the best compromise in terms of converting these to HEVC/MPEG4’s encoder quality settings as compared to the data savings.

  The media collection of TV shows/movies, I don’t mind too much about losing some quality but the home videos/VHS tapes I have in old file formats, the storage factor for these is less important but I was wondering what I’d need to do to convert old AVI’s/MPEG2’s to MPEG4/HEVC - mainly if it is possible to convert one of these old video files to a newer format, without loss of quality, I thought the newer video encoding’s had lossless and lossy compression, but I could be completely wrong and don’t know much about video codecs.

  I was more curious on the best solution to do this as, Googling it gives me loads of commercial software and I’d rather have something which I can use command line/programmatically against my entire libraries. I also couldn’t find anything on these commercial sites about the technicals of re-encoding video so, was wondering if anyone had any experience with any command line applications/have an understanding of the video codecs.