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• FFmpeg decoding H264

  25 septembre 2011, par Steve McFarlin

  I am decoding a H264 stream using FFmpeg on the iPhone. I know the H264 stream is valid and the SPS/PPS are correct as VLC, Quicktime, Flash all decode the stream properly. The issue I am having on the iPhone is best shown by this picture.

  

  It is as if the motion vectors are being drawn. This picture was snapped while there was a lot of motion in the image. If the scene is static then there are dots in the corners. This always occurs with predictive frames. The blocky colors are also an issue.

  I have tried various build settings for FFmpeg such as turning off optimizations, asm, neon, and many other combinations. Nothing seems to alter the behavior of the decoder. I have also tried the Works with HTML, Love and Peace releases, and also the latest GIT sources. Is there maybe a setting I am missing, or maybe I have inadvertently enabled some debug setting in the decoder.

  Edit

  I am using sws_scale to convert the image to RGBA. I have tried various different pixel formats with the same results.

  sws_scale(convertCtx, (const uint8_t**)srcFrame->data, srcFrame->linesize, 0, codecCtx->height, dstFrame->data, dstFrame->linesize);

  I am using PIX_FMT_YUV420P as the source format when setting up my codec context.

• FFMPEG/FFPLAY Dual screen with live RTMP Filter

  28 février 2016, par Dennis Bijsterveld

  What I’m trying to do is getting a RTMP input and apply 2 filters to the same input source and having them next to eachother. To check both EBUR128 levels and waveforms. Problem that I’m getting is that I can’t mix them together.

  Filters :
  EBU R128 (I would love to have a graphical EBU R128 meter.)
  Example :

  ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18
  [out0][out1]"

  And a waveform to check broadcast levels.

  ffplay -i http://download.blender.org/peach/bigbuckbunny_movies/big_buck_bunny_480p_surround-fix.avi -vf "split[a][b] ;[a]format=gray,waveform,split[c][d] ;[b]pad=iw:ih+256[padded] ;[c]geq=g=1:b=1[red] ;[d]geq=r=1:b=1,crop=in_w:220:0:16[mid] ;[red][mid]overlay=0:16[wave] ;[padded][wave]overlay=0:H-h"

• Empty output when extracting frames with FFMPEG at specific timestamps taken from FFPROBE

  9 octobre 2023, par Andrew McDowell

  I am trying to extract frames from a video as close as possible to specific timestamps, but for some timestamps I'm getting no output.

  


  I'm first using ffprobe to get a list of all frames along with their time values :

  


  ffprobe -select_streams v -show_frames -show_entries frame=pts_time,pkt_pts_time,pict_type <input video="video" />

  


  Which gives me an output like :

  


  [FRAME]
pts_time=11.950000
pict_type=I
[/FRAME]
[FRAME]
pts_time=11.966667
pict_type=B
[/FRAME]
[FRAME]
pts_time=11.983333
pict_type=P
[/FRAME]


  


  I'm then parsing this and determining which frame is the closest to the time I want and using FFmpeg to extract frames which match the chosen times like so :

  


  ffmpeg -i <input video="video" /> -filter:v "select=&#x27;eq(t, 11.950000)&#x2B;eq(t, 11.983333)&#x27;" -vsync drop -start_number 0 <output path="path">/frame-%08d.png</output>

  


  This mostly works but I've noticed for some frames I get no output. From some testing it always seems to work for I frames and works occasionally for P or B frames but not always.

  


  I can't see any pattern to which frames it works for or not and would love an insight into whether I'm doing something wrong in the extraction, or whether there's a way to determine which frames can be extracted or not.