Answers.Body: <p>Since it also happens with <code>-f null</code>, but not with another Codec, the CPU load during the capture is a possible explanation. You did not mention it in your question. Is there any specific reason to use <code>-threads 4</code>? Try raising that number or omit the parameter.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2017-05-02T21:23:15.923Z
Answers.LastActivityDate: 2019-12-20T20:47:14.813Z
Answers.LastEditDate: 2019-12-20T20:47:14.813Z
Answers.UserDisplayName: Roy D'atze
Body: <p>I've been using the following command to capture video with ffmpeg for the past two months using my Blackmagic Intensity Pro 4K capture card:</p>
  
  <p><code>ffmpeg -bm_v210 1 -rtbufsize 1500M -threads 4 -f decklink -i "Intensity Pro 4K@20" -c:a copy -c:v prores -profile:v 1 movie1.mov</code></p>
  
  <p>This has been fine although occasionally I get a "Decklink input buffer overrun!" error, in which case I have to restart the capture.</p>
  
  <p>However, starting yesterday, I am getting a "Desklink input buffer overrun!" error every time.</p>
  
  <pre><code>[decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=479405.2kbits/s speed=0.849x
      Last message repeated 1 times
  [decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=480001.5kbits/s speed=0.842x
      Last message repeated 8 times
  [decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=480685.0kbits/s speed=0.842x
      Last message repeated 15 times
  </code></pre>
  
  <p>So it looks like my SSD is no longer fast enough to write the data-- but why?  It worked fine for the past two months.</p>
  
  <p>I'm capturing onto a Sandisk Extreme Pro SSD (960 GB).  The drive only has 10GB of data on it.  I manually ran TRIM just a moment ago, but that didn't help.  The SanDisk SSD Dashboard shows it has "99%" life remaining.</p>
  
  <p>I have also disabled OneDrive, Dropbox, and all other software I could find that might write to the system during capture.</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-19T16:49:45.753Z
Comments.Text: Replace `movie1.mov` with `-map 0 -f null -` to see if it's disk-related. Note: no file will be saved, so this is just for testing purposes.
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-19T16:58:16.157Z
Comments.Text: @Mulvya When I make the replacement, I get the same error.  What does that mean?
Comments.UserDisplayName: Patrick Kenny
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-19T17:21:51.993Z
Comments.Text: More info: When I capture to dnxhr (hq) instead of prores (lt), even though the dnxhr bitrate is ~850000 kbit/sec vs ~450000 kbit/sec for prores, dnxhr works, but not prores.
Comments.UserDisplayName: Patrick Kenny
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-19T17:32:15.707Z
Comments.Text: What's your ffmpeg version?
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-19T17:49:07.670Z
Comments.Text: 3.2.0.  Can't use the builds of 3.2.2 or 3.2.4 because the "enable_decklink" flag isn't turned on so the capture card doesn't work.
Comments.UserDisplayName: Patrick Kenny
Tags: <ffmpeg><video-capture><capturing>
Title: ffmpeg: Why did my capture speed drop? (can no longer capture using same command)
UserDisplayName: Patrick Kenny
ThreadText: # ffmpeg: Why did my capture speed drop? (can no longer capture using same command)
  
  (Asked by: username_0 on 2017-04-19)
  
  I've been using the following command to capture video with ffmpeg for the past two months using my Blackmagic Intensity Pro 4K capture card:
  
  `ffmpeg -bm_v210 1 -rtbufsize 1500M -threads 4 -f decklink -i "Intensity Pro 4K@20" -c:a copy -c:v prores -profile:v 1 movie1.mov`
  
  This has been fine although occasionally I get a "Decklink input buffer overrun!" error, in which case I have to restart the capture.
  
  However, starting yesterday, I am getting a "Desklink input buffer overrun!" error every time.
  
  ```
  [decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=479405.2kbits/s speed=0.849x
      Last message repeated 1 times
  [decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=480001.5kbits/s speed=0.842x
      Last message repeated 8 times
  [decklink @ 0000000002552cc0] Decklink input buffer overrun!bitrate=480685.0kbits/s speed=0.842x
      Last message repeated 15 times
  
  ```
  
  So it looks like my SSD is no longer fast enough to write the data-- but why? It worked fine for the past two months.
  
  I'm capturing onto a Sandisk Extreme Pro SSD (960 GB). The drive only has 10GB of data on it. I manually ran TRIM just a moment ago, but that didn't help. The SanDisk SSD Dashboard shows it has "99%" life remaining.
  
  I have also disabled OneDrive, Dropbox, and all other software I could find that might write to the system during capture.
  
  **Tags:** ffmpeg, video-capture, capturing
  
  > **Comments:**
  > **username_1**: Replace `movie1.mov` with `-map 0 -f null -` to see if it's disk-related. Note: no file will be saved, so this is just for testing purposes.  
  > **username_0**: @Mulvya When I make the replacement, I get the same error.  What does that mean?  
  > **username_0**: More info: When I capture to dnxhr (hq) instead of prores (lt), even though the dnxhr bitrate is ~850000 kbit/sec vs ~450000 kbit/sec for prores, dnxhr works, but not prores.  
  > **username_1**: What's your ffmpeg version?  
  > **username_0**: 3.2.0.  Can't use the builds of 3.2.2 or 3.2.4 because the "enable_decklink" flag isn't turned on so the capture card doesn't work.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2017-05-02. Score: 0
  
  Since it also happens with `-f null`, but not with another Codec, the CPU load during the capture is a possible explanation. You did not mention it in your question. Is there any specific reason to use `-threads 4`? Try raising that number or omit the parameter.
  
  
  ---
  
  