fix(session-replay): revert max key-frame interval to once per video segment

[philprime]

📜 Description

Changes the session replay video segment keyframe interval to 1.

💡 Motivation and Context

H.264 uses different types of frames:

• I‑frames are the least compressible but don't require other video frames to decode.
• P‑frames can use data from previous frames to decompress and are more compressible than I‑frames.

In #5134 we introduced a change in the video segment configuration to only use I-Frame by setting AVVideoMaxKeyFrameIntervalKey to increase (browser) compatibility.

Further testing surfaced now that the browser compatibility is not affected by this option, but it increases the file size of video segments:

$ ffprobe -select_streams v:0 -show_frames -show_entries frame=pict_type,coded_picture_number -of csv -hide_banner pre-5134.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'older.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: isommp41mp42
    creation_time   : 2025-04-24T14:50:59.000000Z
  Duration: 00:00:05.00, start: 0.000000, bitrate: 14 kb/s
  Stream #0:0[0x1](und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, progressive), 393x852 [SAR 1:1 DAR 131:284], 13 kb/s, 1 fps, 1 tbr, 600 tbn (default)
      Metadata:
        creation_time   : 2025-04-24T14:50:59.000000Z
        handler_name    : Core Media Video
        vendor_id       : [0][0][0][0]
frame,I,H.26[45] User Data Unregistered SEI message
frame,P,H.26[45] User Data Unregistered SEI message
frame,P,H.26[45] User Data Unregistered SEI message
frame,P,H.26[45] User Data Unregistered SEI message
frame,P,H.26[45] User Data Unregistered SEI message

$ ffprobe -select_streams v:0 -show_frames -show_entries frame=pict_type,coded_picture_number -of csv -hide_banner post-5134.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'newer.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 1
    compatible_brands: isommp41mp42
    creation_time   : 2025-04-24T14:49:05.000000Z
  Duration: 00:00:05.00, start: 0.000000, bitrate: 31 kb/s
  Stream #0:0[0x1](und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 393x852 [SAR 1:1 DAR 131:284], 29 kb/s, 1 fps, 1 tbr, 600 tbn (default)
      Metadata:
        creation_time   : 2025-04-24T14:49:05.000000Z
        handler_name    : Core Media Video
        vendor_id       : [0][0][0][0]
frame,I,H.26[45] User Data Unregistered SEI message
frame,I,H.26[45] User Data Unregistered SEI message
frame,I,H.26[45] User Data Unregistered SEI message
frame,I,H.26[45] User Data Unregistered SEI message
frame,I,H.26[45] User Data Unregistered SEI message

The actual difference in size varies depending on the amount of changes in the video, but we could see up to 100% larger sizes.

Using the latest changes on main this replay works in Chrome, Firefox and Safari.

💚 How did you test it?

For this replay I changed I-Frames interval to 6 (1 I-Frame per 5 second video segment at 1 FPS, the others are P-Frames) which reduced the size from 19KB to 6KB for the first segment, while it still works in all browsers.

📝 Checklist

You have to check all boxes before merging:

• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.782%. Comparing base (c40037e) to head (08dfa4f).
Report is 5 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #5156       +/-   ##
=============================================
+ Coverage   92.774%   92.782%   +0.007%     
=============================================
  Files          677       677               
  Lines        84275     84270        -5     
  Branches     30658     30645       -13     
=============================================
+ Hits         78186     78188        +2     
+ Misses        5987      5980        -7     
  Partials       102       102               

Files with missing lines	Coverage Δ
...egrations/SessionReplay/SentryOnDemandReplay.swift	93.538% <100.000%> (+0.019%)	⬆️
...ions/SessionReplay/SentryOnDemandReplayTests.swift	92.792% <100.000%> (ø)

... and 16 files with indirect coverage changes

---

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	1233.62 ms	1251.70 ms	18.08 ms
Size	22.30 KiB	850.93 KiB	828.62 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
c6504da	1232.06 ms	1243.28 ms	11.22 ms
c6b920a	1239.53 ms	1256.53 ms	17.00 ms
318a891	1245.14 ms	1259.02 ms	13.88 ms
5e769dd	1216.24 ms	1245.74 ms	29.50 ms
7cd187e	1243.04 ms	1244.79 ms	1.75 ms
4329cdb	1206.96 ms	1227.74 ms	20.78 ms
6813f7c	1232.23 ms	1251.47 ms	19.24 ms
4350d44	1228.75 ms	1246.75 ms	18.00 ms
a176fc4	1226.24 ms	1247.50 ms	21.26 ms
25bcc50	1237.69 ms	1258.40 ms	20.71 ms

App size

Revision	Plain	With Sentry	Diff
c6504da	20.76 KiB	414.44 KiB	393.69 KiB
c6b920a	21.58 KiB	631.19 KiB	609.61 KiB
318a891	22.30 KiB	750.02 KiB	727.72 KiB
5e769dd	21.58 KiB	572.21 KiB	550.62 KiB
7cd187e	20.76 KiB	401.65 KiB	380.89 KiB
4329cdb	22.30 KiB	833.10 KiB	810.80 KiB
6813f7c	21.58 KiB	614.86 KiB	593.28 KiB
4350d44	21.58 KiB	629.82 KiB	608.24 KiB
a176fc4	22.84 KiB	403.24 KiB	380.39 KiB
25bcc50	20.76 KiB	427.23 KiB	406.46 KiB