<p>It sounds like you're analyzing a HEVC bitstream. HEVC has multiple types of Random Access Pictures, only one of which clears the buffer. But ffmpeg flags all of them as keyframes.</p>

<p>You have to use the HEVC decoder to parse this info out. The skip_frame option, as implemented in the HEVC decoder, only decodes IDR frames.</p>

<p>Use</p>

<pre><code>ffmpeg -skip_frame nokey -i in.mp4 -vf showinfo -vsync 0 -f null -
</code></pre>

<p>The number of frames output is the IDR count.</p>

<hr>

<p>For the sample file, you can use the filter_units bitstream filter to keep only IDR frames</p>

<pre><code>ffmpeg -copyts -i HEVC-1080i25-STB_02_576i25.ts -an -c copy -bsf:v filter_units="19-20" -f mpegts - | ffmpeg -copyts -i - -vf showinfo -f null NUL
</code></pre>

<p>This will show the data of 118 frames, same as the analyzer.</p>

CC BY-SA 3.0
2018-03-23T11:42:27.763Z
Thanks for your response.                                                                   This issue is there for AVC content  as well.  Actually i need to grab pts values for each IDR frame
Ashok
CC BY-SA 3.0
2018-03-23T12:38:33.883Z
I did a source check and AVC decoder appears to work the same way. Added filter in command to display PTS.
Gyan
CC BY-SA 3.0
2018-03-27T14:00:14.487Z
Hi it works fine only with interlaced output this issue is still there for progressive
Ashok
CC BY-SA 3.0
2018-03-27T15:09:55.957Z
The issue is ffmpeg iskey value is set to 1 for CRA frames as well. (Instantaneous Decoder Refresh (IDR), Clean Random Access (CRA), I need to collect only IDR frames
Ashok
CC BY-SA 3.0
2018-03-27T16:08:22.793Z
Let me test this. Can you share a HEVC stream along with Tektronix results for it.
Gyan
CC BY-SA 3.0
2018-03-27T21:00:56.630Z
I see only upload image option, Where can i upload stream, ??
Ashok
CC BY-SA 3.0
2018-03-28T05:49:14.837Z
To some file-sharing service and post links
Gyan
CC BY-SA 3.0
2018-03-28T08:21:44.013Z
1. HEVC Progressive Stream : http://www.mediafire.com/file/4t2ujzf708ippca/HEVC-1080i25-STB_02_576i25.ts   
2. HEVC Progressive textronic analyzer : http://www.mediafire.com/file/5ayuwtztwtwtig1/HEVC-1080p25-STB_02_576p25.txt
Ashok
CC BY-SA 3.0
2018-04-05T13:45:22.220Z
@Mulya updated the stream and textronix analysis results, please have a look and let me know if you need any more information. It will be really great if i could get some help
Ashok
CC BY-SA 3.0
2018-04-17T07:25:57.360Z
"The issue is ffmpeg iskey value is set to 1 for CRA frames as well. I need to collect only IDR frames "  Can anyone help me on this issue??
Ashok
CC BY-SA 3.0
2018-04-17T07:37:17.610Z
Sorry; forgot about this. Will look into it.
Gyan
CC BY-SA 3.0
2018-04-20T18:00:35.877Z
See new command.
Gyan
CC BY-SA 3.0
2018-03-22T16:49:45.060Z
2018-04-20T18:00:26.993Z
2018-04-20T18:00:26.993Z
Gyan
<p><a href="https://i.sstatic.net/YQlvS.jpg" rel="noreferrer"><img src="https://i.sstatic.net/YQlvS.jpg" alt="enter image description here"></a>How does ffprobe identifies I frame as an IDR and sets <code>key_frame=1</code>.
Is it for the scene change?</p>

<p>My requirement is to filter out IDR frames: the steps I am following are</p>

<ol>
<li><code>ffprobe output_file -show_frames -select_streams v:0</code></li>
<li>Filter above command results with <code>key_frame=1</code> values(as per ffprobe IDR)</li>
<li>The total count i got is 259. Using ffprobe I am getting wrong sets of <code>key_frame=1</code> values.</li>
<li>When i analyzed the same file with textronic analyzer I got correct values <code>idr = 118</code></li>
</ol>

<p>Textronix analyzer gives me below details for a a file verification.</p>

<pre><code>TotalPictures:Count[ 5864]
I Pictures: Count[  259]
P Pictures: Count[ 1059]
B Pictures: Count[ 4546]

RAP Pictures:Count[259]
IDR Pictures:Count[118] 
BLA Pictures:Count[0] 
CRA Pictures:Count[141]

Frames:     Count[ 5864]    Percentage[100.00]
Fields:     Count[    0]    Percentage[0.00]

GOP (in Pictures, between I): Count[258] AverageSize[22] MinSize[1] MaxSize[50]
CVS (in Pictures, between IDR):Count[117] AverageSize[50]MinSize[50]MaxSize[50]
</code></pre>

<p>Now how to identify correct IDR count using ffprobe?</p>

<p>FFmpeg is setting iskey to 1 for CRA frames as well(tried with -skip_frame nokey). I need to collect only IDR frames </p>

<ffmpeg><hevc>
How does ffprobe identifies I frame and IDR, when it sets key_frame=1
Ashok
# How does ffprobe identifies I frame and IDR, when it sets key_frame=1

(Asked by: username_0 on 2018-03-22)

How does ffprobe identifies I frame as an IDR and sets key_frame=1.
Is it for the scene change?
My requirement is to filter out IDR frames: the steps I am following are

ffprobe output_file -show_frames -select_streams v:0
Filter above command results with key_frame=1 values(as per ffprobe IDR)
The total count i got is 259. Using ffprobe I am getting wrong sets of key_frame=1 values.
When i analyzed the same file with textronic analyzer I got correct values idr = 118

Textronix analyzer gives me below details for a a file verification.
TotalPictures:Count[ 5864]
I Pictures: Count[  259]
P Pictures: Count[ 1059]
B Pictures: Count[ 4546]

RAP Pictures:Count[259]
IDR Pictures:Count[118] 
BLA Pictures:Count[0] 
CRA Pictures:Count[141]

Frames:     Count[ 5864]    Percentage[100.00]
Fields:     Count[    0]    Percentage[0.00]

GOP (in Pictures, between I): Count[258] AverageSize[22] MinSize[1] MaxSize[50]
CVS (in Pictures, between IDR):Count[117] AverageSize[50]MinSize[50]MaxSize[50]

Now how to identify correct IDR count using ffprobe?
FFmpeg is setting iskey to 1 for CRA frames as well(tried with -skip_frame nokey). I need to collect only IDR frames

**Tags:** ffmpeg, hevc


---

## 1 answers

### Answer by username_1 on 2018-03-22. Score: 3

It sounds like you're analyzing a HEVC bitstream. HEVC has multiple types of Random Access Pictures, only one of which clears the buffer. But ffmpeg flags all of them as keyframes.
You have to use the HEVC decoder to parse this info out. The skip_frame option, as implemented in the HEVC decoder, only decodes IDR frames.
Use
ffmpeg -skip_frame nokey -i in.mp4 -vf showinfo -vsync 0 -f null -

The number of frames output is the IDR count.

For the sample file, you can use the filter_units bitstream filter to keep only IDR frames
ffmpeg -copyts -i HEVC-1080i25-STB_02_576i25.ts -an -c copy -bsf:v filter_units="19-20" -f mpegts - | ffmpeg -copyts -i - -vf showinfo -f null NUL

This will show the data of 118 frames, same as the analyzer.

> **Comments:**
> **username_0**: Thanks for your response.                                                                   This issue is there for AVC content  as well.  Actually i need to grab pts values for each IDR frame  
> **username_1**: I did a source check and AVC decoder appears to work the same way. Added filter in command to display PTS.  
> **username_0**: Hi it works fine only with interlaced output this issue is still there for progressive  
> **username_0**: The issue is ffmpeg iskey value is set to 1 for CRA frames as well. (Instantaneous Decoder Refresh (IDR), Clean Random Access (CRA), I need to collect only IDR frames  
> **username_1**: Let me test this. Can you share a HEVC stream along with Tektronix results for it.  
> **username_0**: I see only upload image option, Where can i upload stream, ??  
> **username_1**: To some file-sharing service and post links  
> **username_0**: 1. HEVC Progressive Stream : http://www.mediafire.com/file/4t2ujzf708ippca/HEVC-1080i25-STB_02_576i25.ts    2. HEVC Progressive textronic analyzer : http://www.mediafire.com/file/5ayuwtztwtwtig1/HEVC-1080p25-STB_02_576p25.txt  
> **username_0**: @Mulya updated the stream and textronix analysis results, please have a look and let me know if you need any more information. It will be really great if i could get some help  
> **username_0**: "The issue is ffmpeg iskey value is set to 1 for CRA frames as well. I need to collect only IDR frames "  Can anyone help me on this issue??  
> **username_1**: Sorry; forgot about this. Will look into it.  
> **username_1**: See new command.  

---

