[FFmpeg-user] Issue with Delayed Packet Writing to MP4 Container Using Hardware Encoder (h264_v4l2m2m) in FFmpeg API

[Lisa]

After debugging, I found that with the software encoder, the encoded packet
data includes the header information, whereas with the hardware encoder, a
lot of this information is missing.

I tried to debug and print all the AVPacket structure members, but that did
not provide any useful insights. The issue arises when I miss the first
packet while storing it in an MP4 container using the hardware encoder.
This results in the video file becoming corrupt.

https://ffmpeg.org/doxygen/3.2/structAVPacket.html

Is there any approach to solve this issue? Or is there a way to ensure that
the headers in hardware-encoded packets are similar to those in
software-encoded packets? (With the software encoder, there is no issue,
even when we store delayed packets.)

I even tried to hard-code the first packet using data generated by a
software-encoded packet, but that did not work either.

Can anyone please help solve this issue? Where might I be going wrong? Am I
following the correct flow?



On Mon, Jan 27, 2025 at 2:12 PM Lisa <lisas965624 at gmail.com> wrote:

> Hello. I am trying to store the encoded packets to a mp4 container file
> using av_interlenced_write_packet() ffmpeg api.
>
> With Hardware encoder[h264_v4l2m2m] there is an issue when I add 1 second
> delay to write encoded Packets to the mp4 container.
> While writing the packets there are no errors but the encoded video is not
> playing.When verified with *mediainfo* CLI, got some partial metadata
> about the video.
> NOTE: Without delay there is no issue with recorded video.
>
>    - *Mediainfo output of video without delay*
>
> [image: mediainfo_of_no_delay.png]
>
>
>    - *Mediainfo output of video with delay*
>
> [image: mediainfo_of_with_delay.png]
>
>
> The flow of my code is as described in the text and illustrated in the
> flow diagram.
> ...
> ->send packet to encode
> ->Receive packet
> ->then clone the packet with av_packet_clone(sourcePacket)
> ->modified the pts & dts and
> ->writing frames to disk using av_interleaved_write_frame
> <https://www.ffmpeg.org/doxygen/4.0/group__lavf__encoding.html#ga37352ed2c63493c38219d935e71db6c1>
>  (AVFormatContext
> <https://www.ffmpeg.org/doxygen/4.0/structAVFormatContext.html> *s
> <https://www.ffmpeg.org/doxygen/4.0/llviddspenc_8c.html#a517a4433fe5466cc6af1c80c538b0881>
> , AVPacket <https://www.ffmpeg.org/doxygen/4.0/structAVPacket.html> *pkt
> <https://www.ffmpeg.org/doxygen/4.0/demuxing__decoding_8c.html#a3d4c6562f0b27cf0cacbbea5c038c090>
> )
> ...
> [image: ffmpeg.png]
>
>    1. Why is the issue occurring with a delay of about 1 second?
>    2. How can this issue be resolved?
>
>
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: mediainfo_of_no_delay.png
Type: image/png
Size: 150244 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-user/attachments/20250305/65d0d6b2/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: mediainfo_of_with_delay.png
Type: image/png
Size: 107259 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-user/attachments/20250305/65d0d6b2/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ffmpeg.png
Type: image/png
Size: 67083 bytes
Desc: not available
URL: <https://ffmpeg.org/pipermail/ffmpeg-user/attachments/20250305/65d0d6b2/attachment-0002.png>