Answers.Body: <p>Audio data consists of samples. The sampling rate indicates the number of samples per channel in one second. But when dealing with audio, applications read and process samples in chunks. These chunks are the frames. The AAC encoder uses 1024 Samples Per Frame. So, the audio &quot;Frame Rate&quot; is Sampling rate/1024 for AAC audio. This is not related to video frame rate.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2022-02-01T04:30:22.897Z
Answers.LastActivityDate: 2022-02-01T04:30:22.897Z
Answers.UserDisplayName: Gyan
Body: <p>I am doing some transcoding via ffmpeg and am noticing video and audio FPS differing greatly. During playback there is no issue, everything is working as expected. So I am trying to understand what it means for audio to be at much higher framerate and how audio is not going out of sync due to that?</p>
  <p>Thank you.</p>
  <pre><code>Video
  ID                                       : 1
  Format                                   : AVC
  Format/Info                              : Advanced Video Codec
  Format profile                           : High@L3
  Format settings                          : CABAC / 4 Ref Frames
  Format settings, CABAC                   : Yes
  Format settings, ReFrames                : 4 frames
  Codec ID                                 : V_MPEG4/ISO/AVC
  Duration                                 : 46 min 12 s
  Width                                    : 852 pixels
  Height                                   : 480 pixels
  Display aspect ratio                     : 16:9
  Frame rate mode                          : Constant
  Frame rate                               : 23.976 (24000/1001) FPS
  Color space                              : YUV
  Chroma subsampling                       : 4:2:0
  Bit depth                                : 8 bits
  Scan type                                : Progressive
  Writing library                          : x264 core 152 r2854 e9a5903
  Encoding settings                        : cabac=1 / ref=1 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=2 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=9 / lookahead_threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=10 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
  Default                                  : Yes
  Forced                                   : No
  
  Audio
  ID                                       : 2
  Format                                   : AAC
  Format/Info                              : Advanced Audio Codec
  Format profile                           : LC
  Codec ID                                 : A_AAC-2
  Duration                                 : 46 min 12 s
  Channel(s)                               : 2 channels
  Channel positions                        : Front: L R
  Sampling rate                            : 48.0 kHz
  Frame rate                               : 46.875 FPS (1024 SPF)
  Compression mode                         : Lossy
  Delay relative to video                  : -104 ms
  Writing library                          : Lavc57.107.100 aac
  Language                                 : English
  Default                                  : Yes
  Forced                                   : No
  </code></pre>
  
Tags: <ffmpeg><audio><framerate>
Title: What is the meaning behind video and audio framerates being different?
UserDisplayName: Duxa
ThreadText: # What is the meaning behind video and audio framerates being different?
  
  (Asked by: username_0 on 2022-01-31)
  
  I am doing some transcoding via ffmpeg and am noticing video and audio FPS differing greatly. During playback there is no issue, everything is working as expected. So I am trying to understand what it means for audio to be at much higher framerate and how audio is not going out of sync due to that?
  
  Thank you.
  
  ```
  Video
  ID                                       : 1
  Format                                   : AVC
  Format/Info                              : Advanced Video Codec
  Format profile                           : High@L3
  Format settings                          : CABAC / 4 Ref Frames
  Format settings, CABAC                   : Yes
  Format settings, ReFrames                : 4 frames
  Codec ID                                 : V_MPEG4/ISO/AVC
  Duration                                 : 46 min 12 s
  Width                                    : 852 pixels
  Height                                   : 480 pixels
  Display aspect ratio                     : 16:9
  Frame rate mode                          : Constant
  Frame rate                               : 23.976 (24000/1001) FPS
  Color space                              : YUV
  Chroma subsampling                       : 4:2:0
  Bit depth                                : 8 bits
  Scan type                                : Progressive
  Writing library                          : x264 core 152 r2854 e9a5903
  Encoding settings                        : cabac=1 / ref=1 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=2 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=9 / lookahead_threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=10 / rc=crf / mbtree=1 / crf=23.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
  Default                                  : Yes
  Forced                                   : No
  
  Audio
  ID                                       : 2
  Format                                   : AAC
  Format/Info                              : Advanced Audio Codec
  Format profile                           : LC
  Codec ID                                 : A_AAC-2
  Duration                                 : 46 min 12 s
  Channel(s)                               : 2 channels
  Channel positions                        : Front: L R
  Sampling rate                            : 48.0 kHz
  Frame rate                               : 46.875 FPS (1024 SPF)
  Compression mode                         : Lossy
  Delay relative to video                  : -104 ms
  Writing library                          : Lavc57.107.100 aac
  Language                                 : English
  Default                                  : Yes
  Forced                                   : No
  
  ```
  
  **Tags:** ffmpeg, audio, framerate
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2022-02-01. Score: 1 | Accepted answer
  
  Audio data consists of samples. The sampling rate indicates the number of samples per channel in one second. But when dealing with audio, applications read and process samples in chunks. These chunks are the frames. The AAC encoder uses 1024 Samples Per Frame. So, the audio "Frame Rate" is Sampling rate/1024 for AAC audio. This is not related to video frame rate.
  
  
  ---
  
  