[Question] Fragmented recording

[alexsafe]

Hi Pedro,

I did almost 0 homework before asking this, so appologies in advance :)

My question is: is it possible to have a way to protect a recording from unforseen events. Like a sudden app close mid-recording. That would corrupt the mp4. The muxer stop/release are most likely not called.

So is it possible to save in chunks in a way that the MOOV is written?
Or, a workaround that I did think about was to try to record in chunks of say separate 10s files and then have them stitched together at stopRecord() with ffmpeg. I'm already using it so that part won't be a too big of an overhead for me.

Do you think one if these 2 options would work or do you have another suggestion?

Thanks!

[pedroSG94]

Hello,

Currently the record use MediaMuxer by default that no allow record in chunks. With MediaMuxer you need stop and start again to create a new file and always need start with a key frame so you can lose few frames while the keyframe is generated.
Possible solutions.

• Use FlvMuxerRecordController and record FLV files and If you require a mp4 you can convert it after record with ffmpeg. The problem is that this class format only support H264, AAC, OPUS and G711
• Modify the library to use WEBM format (this support VP8, VP9 and OPUS but require implement a way to support VP8 and VP9 encoding)
• Create a custom RecordController class to support your case using other classes to create the file.

[alexsafe]

hey, thanks for the suggestions! Between flv and vp9 i think vp9 fits way better for our use case. We are looking for high quality recordings but file sizes matter. So i guess implementing WEBM would be the way to go. But then there are playback limitations on ios and I'm not sure how important that part is. For the 3rd possible solution you mean the approach where I stop and start recordings? Losing frames doesn't sound too good. we are aiming for crisp recordings. Do you know if the frame losses would be visible at playback? 1,2 missing frames would probably be fine?

…

On Thu, Nov 27, 2025, 04:00 Pedro Sánchez ***@***.***> wrote: *pedroSG94* left a comment (pedroSG94/RootEncoder#1987) <#1987 (comment)> Hello, Currently the record use MediaMuxer by default that no allow record in chunks. With MediaMuxer you need stop and start again to create a new file and always need start with a key frame so you can lose few frames while the keyframe is generated. Possible solutions. - Use FlvMuxerRecordController and record FLV files and If you require a mp4 you can convert it after record with ffmpeg. The problem is that this class format only support H264, AAC, OPUS and G711 - Modify the library a bit to use WEBM format (this support VP8, VP9 and OPUS but require implement a way to support VP8 and VP9 encoding) - Create a custom RecordController class to support your case using other classes to create the file. — Reply to this email directly, view it on GitHub <#1987 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABHY7RNDYNV5NR6CSC2GIVL3624SLAVCNFSM6AAAAACNJTGFXOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTKOBUHAYTKMZXGA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[pedroSG94]

For now if the codec is not a limitation for you, you should start with the case 1 and I will try implement case 2.
About the case 3, it is basically develop a new class for record that could use ffmpeg or other libraries to record instead of MediaMuxer that is limited for your case.

[alexsafe]

Ok got it. Thanks for looking into implementing webm.
I think ffmpeg recording would ultimately result in heavy use of the CPU, right? like for 1,2 3h of continuous recording would result in all kinds of thermal issues and heavy battery use and so on.

I'll check for flv and also into recording in chunks with stop/start and then putting those file together with ffmpeg. I think that would be less intense than directly recording with ffmpeg. I think the way to go in this case woudl be to keep the camera session and encoder running and just close and open files with the Muxer.

[pedroSG94]

FLV no need create chunks because it doesn't need close the file. So the file can't be corrupt for that reason if the app crash or something happens.

I was looking about this case a bit more but webm can be discarded because this format can be corrupt if the mediamuxer is not closed (exactly like mp4).
My recommendation is record in FLV and then if you want reduce the file size you can use ffmpeg to re-encode in other format after that.

I did the support of H265 and AV1 codec in FLV record here:
#1998

Right now, this codec in FLV is not supported in all players but could help you. For now, I only found that ffmpeg support it. I'm using Ubuntu 24.04.3 LTS with this version of ffmpeg:
ffplay version 6.1.1-3ubuntu5 Copyright (c) 2003-2023 the FFmpeg developers built with gcc 13 (Ubuntu 13.2.0-23ubuntu3)

[alexsafe]

Sweet, thanks! Is it "real" H265 support? Becuase I read that flv doesn't natively support H265.
I'll give it a try and make some comparisons with H264.

For ffmpeg, it would have to be implemented in the app. So after the recording is done I could some operations there if needed.
The use case is for the situation when the app crashes (battery 0% or whatever else) such that the recording survives this. If I'll need to process the flv after it will have to be done when the app is online again (assuming the worst case scenario)

In the meantime I've worked on the other idea with recording in chunks of 20 seconds (or whatever) using the Muxer and then concatenating them with ffmpeg. The downside would be losing the last x seconds of the recording. But it seems to work pretty well. Still working on it but the results seem ok. Will keep you updated.

[pedroSG94]

Hello,

The H265 and AV1 support use this standard:
https://github.com/veovera/enhanced-rtmp

Now it is officially supported by many platforms like YouTube (actually supporting rtmp with H265 and AV1).
Also, I added Opus support but it isn't really extended yet because it is supported only in the v2 of the standard so I don't recommend you use Opus for now.