ffmpeg MKV to MP4 error track 1: codec frame size is not set

[Anonymous543]

hello there i have a movie clip which is in mkv container

i separated its video with following code

ffmpeg -i input.mkv -c:v copy -an video.mkv

and also separated its audio with following code

ffmpeg -i input.mkv -vn -c:a copy audio.ac3

after that i rencoded video with 2 pass rate control mode using this code

ffmpeg -y -i video.mkv -c:v libx264 -vf scale=426:240 -b:v 400k -pass 1 -f null NUL && ^
ffmpeg -i video.mkv -c:v libx264 -vf scale=426:240 -b:v 400k -pass 2 v.mkv

and also rencoded audio with this code

ffmpeg -i audio.ac3 -ac 2 -c:a libopus -b:a 128k a.opus

now i have 2 separated file
v.mkv = contains only video
a.opus = contains only audio
too combine them in mp4 i used this code

ffmpeg -i v.mkv -i a.opus -c copy clip.mp4

but it gave me this results

[Attachment 63598 - Click to enlarge]

[Attachment 63599 - Click to enlarge]






when i combine them in mkv it does not shows any yellow line that track 1: codec frame size is not set

but i want my final clip in mp4 without that yellow line
how can i fix this?

[Anonymous543]

when i done encoding with same settings on my source input.mkv(without separating audio and video) using this code

ffmpeg -y -i input.mkv -vf scale=426:240 -c:v libx264 -preset ultrafast -b:v 400k -pass 1 -an -f null NUL && ^
ffmpeg -i input.mkv -vf scale=426:240 -c:v libx264 -preset ultrafast -b:v 400k -pass 2 -ac 2 -filter:a "volume=1.2" -c:a libopus -b:a 128k output.mp4

this was successfull without any yellow lines


when i watched mediainfo of both encoding outputs..
1st output.mp4 which i got by separating audio and video then rencoded with yellow line error
2nd output.mp4 which was directly done to source

both outputs mediainfo is almost same

[Selur]

try creating the audio inside a mkv container instead of writing it to a raw opus file.
My guess is the warning happens since ffmpeg isn't totally sure that the .opus stream does not contain just audio.

Cu Selur

[Anonymous543]

try creating the audio inside a mkv container instead of writing it to a raw opus file.
My guess is the warning happens since ffmpeg isn't totally sure that the .opus stream does not contain just audio.

Cu Selur

i created audio in mkv container using this code

ffmpeg -i audio.ac3 -c:a libopus -b:a 128k a.mkv

then combined with my v.mkv(my video)in mp4 container with this code

ffmpeg -i v.mkv -i a.mkv -c copy clip.mp4

still its showing same yellow line.

[Anonymous543]

will that yellow line cause any latency in my audio track or any bad affect on my output any way?

[Selur]

will that yellow line cause any latency in my audio track or any bad affect on my output any way?

I don't think so.

[Anonymous543]

still its a mystery, why this problem occurring while combining h264 video stream and opus audio stream in mp4 wrapper

[october262]

still its a mystery, why this problem occurring while combining h264 video stream and opus audio stream in mp4 wrapper

try with ffmpeg -i example.mkv -c copy out.mp4

[Anonymous543]

still its a mystery, why this problem occurring while combining h264 video stream and opus audio stream in mp4 wrapper

try with ffmpeg -i example.mkv -c copy out.mp4

It will be successful..
But if the
h264video.mkv(or any wrapper)(only video stream) and
lipopus.opus(only audio stream)

Are separated
Then

ffmpeg -i h264video.mkv -i libopus.opus -c copy output.MP4

Will not work properly ,it will end with track :1 codec frame size is not set

[october262]

still its a mystery, why this problem occurring while combining h264 video stream and opus audio stream in mp4 wrapper

try with ffmpeg -i example.mkv -c copy out.mp4

It will be successful..
But if the
h264video.mkv(or any wrapper)(only video stream) and
lipopus.opus(only audio stream)

Are separated
Then

ffmpeg -i h264video.mkv -i libopus.opus -c copy output.MP4

Will not work properly ,it will end with track :1 codec frame size is not set

this here - https://holtstrom.com/michael/blog/post/517/MKV-to-MP4.html
says to use -acodec ac3 instead of -acodec copy it should solve your codec frame size is not set error

[Anonymous543]

But i want my final output in MP4 container with libx264 as my video codec and libopus as my audio codec

[Anonymous543]

https://askubuntu.com/questions/768762/combine-h-264-video-and-opus-audio-stream-into-...audio%20tracks.

According to this website MP4 can't have opus audios with h264 video



After checking that website i readed about opus in Wikipedia
https://en.m.wikipedia.org/wiki/Opus_(audio_format)

Opus is Contained by
Ogg, Matroska, WebM, MPEG-TS

May be that's why MP4 is having issues with Opus audio track in ffmpeg

[Selur]

You could use mp4box,...

[Anonymous543]

You could use mp4box,...

May be Opus and h264 together in MP4 wrapper isn't a good option or may be there's a some reason that's why ffmpeg is showing yellow line..and gpac mp4box i never used but it's based on ffmpeg i guess

[Selur]

gpac mp4box i never used but it's based on ffmpeg i guess

No, it's not. (I mainly use MP4Box and rarely use ffmpeg.)

[Anonymous543]

No, it's not. (I mainly use MP4Box and rarely use ffmpeg.)

Thanks for suggestion

But i still wanna know why ffmpeg is giving yellow line..
We can combine audio + video streams in mkv wrapper without yellow line ,
We can also combine them in mp4 wrapper but it gives yellow line ,i think it's ffmpeg bug or something is going wrong may be container issue or something else

There's one report on same issue on ffmpeg website here
https://ffmpeg.org/pipermail/ffmpeg-user/2018-February/038999.html

They suggested to rencode audio stream instead of copying codecs..but why it will need when my audio stream is already encoded in opus

[Selur]

You either need to reade the source code or ask the ffmpeg developers about it.

[Anonymous543]

I don't know any ffmpeg developer and how to contact them ,but i know that gyan and btbn compiles ffmpeg builds ,may be gyan will know about it

[Selur]

ffmpeg bug tracker (https://trac.ffmpeg.org/) or the mailing list you youself linked to might be a good place to contact the ffmpeg authors.

[Anonymous543]

ffmpeg bug tracker (https://trac.ffmpeg.org/) or the mailing list you youself linked to might be a good place to contact the ffmpeg authors.

Thanks✨

[Gyan]

The MP4 writer tries to determine if the audio track is VBR, for the purposes of the some of the further metadata it has to write. It checks the encoded audio frame size as part of that. The MKV writer does not do this.

Since you're remuxing, that data isn't available for Opus, so the writer complains. But there is no deficiency with the file.

I'll change the log level for that message - not really something for general users to be concerned with.

[Anonymous543]

The MP4 writer tries to determine if the audio track is VBR, for the purposes of the some of the further metadata it has to write. It checks the encoded audio frame size as part of that. The MKV writer does not do this.

Since you're remuxing, that data isn't available for Opus, so the writer complains. But there is no deficiency with the file.

I'll change the log level for that message - not really something for general users to be concerned with.

(am not sure)it can be problematic if we change remux audio which is also resampled..then maybe resampled audio framesize will be changed and can cause audio track end before video ends or can cause latency in track in short it cant be sync properly i guess..


what if sourceaudiovideo is not separated and rencoded together

It checks the encoded audio frame size as part of that

then this data will be available for mp4 writter?

[Gyan]

The decoder will pick up the frame size from the stream itself.

Yes, if there's an Opus encoder running in the process, it will fill out the frame size.

[Anonymous543]

Thanks for explaination✨