<div><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">---------- Пересылаемое сообщение ---------<br>От: <strong class="gmail_sendername" dir="auto">Yurii Monakov</strong> <span dir="auto"><<a href="mailto:monakov.y@gmail.com">monakov.y@gmail.com</a>></span><br>Дата: Чт, 2 марта 2023 г. в 15:47<br>Тема: Re: [Libav-user] How to free an AVBuffer?<br>Кому: Wladislav Artsimovich <ffmpeg@frost.kiwi><br></div><br><br><div dir="ltr"><div>Vlad,</div><div><br></div><div>What is the lifetime of your frame? If it is persistent across calls then you allocate</div><div>new side data in every call and ffmpeg simply grows its side data list.</div><div><br></div><div>You can use av_frame_new_side_data, copy data to it, send a frame to codec and</div><div>then av_frame_remove_side_data. There is no need to allocate a separate buffer,</div><div>av_frame_new_side_data does this internally.<br></div><div><br></div><div>If you wish to save some allocations, you need to check if side data of a given</div><div>type is already present. If message.Length changes from call to call, you have to</div><div>av_buffer_realloc <span>sideData-></span>buf and fix <span>sideData-></span>data/<span>sideData->size fields.</span></div><div><span><br></span></div><div><span>Regards,<br></span></div><div><span>Yurii<br></span></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">чт, 2 мар. 2023 г. в 07:06, Wladislav Artsimovich <ffmpeg@frost.kiwi>:<br></div></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">Dear Yurii,<br>
<br>
thx for elaborating. Indeed reassigning the pointer was a logical error, <br>
thx for pointing (hah) it out. I tried using `av_buffer_create()` <br>
originally, but couldn't find a way of using that function pointer <br>
callback `av_buffer_default_free()` in C#.<br>
From C# pMessageData cannot be freed, but is discarded automatically <br>
when the fixed{} block ends. I managed to free that MetaDatabuffer and <br>
the associated memory leak is gone! But not via `av_free()` (which <br>
didn't work, no error, no freeing), but via `av_buffer_unref()`. <br>
However, there still remains another memory leak caused by <br>
`av_frame_new_side_data_from_buf()`<br>
<br>
How can I solve that? I tried following <br>
<a href="https://chromium.googlesource.com/chromium/third_party/ffmpeg/+/refs/heads/master/libavutil/frame.c#66" rel="noreferrer" target="_blank">https://chromium.googlesource.com/chromium/third_party/ffmpeg/+/refs/heads/master/libavutil/frame.c#66</a> <br>
and inserting `ffmpeg.av_buffer_unref(&sideData->buf); <br>
ffmpeg.av_dict_free(&sideData->metadata); ffmpeg.av_freep(sideData);` at <br>
different positions and `av_frame_remove_side_data()` at different <br>
positions, eg. before or after `ffmpeg.av_packet_free(&pPacket);`. The <br>
Encoder just gracefully stops without error, not processing any further <br>
frames.<br>
<br>
What would be the proper procedure to free that AVFrameSideData?<br>
<br>
Here is the full breakdown:<br>
<br>
0 MB memory leaked per 100000 frames:<br>
fixed (byte* pMessageData = message)<br>
{<br>
//AVBufferRef* MetaDataBuffer = <br>
ffmpeg.av_buffer_alloc((ulong)message.Length);<br>
//System.Buffer.MemoryCopy(pMessageData, MetaDataBuffer->data, <br>
(ulong)message.Length, (ulong)message.Length);<br>
//AVFrameSideData* sideData = <br>
ffmpeg.av_frame_new_side_data_from_buf(&frame, <br>
AVFrameSideDataType.AV_FRAME_DATA_SEI_UNREGISTERED, MetaDataBuffer);<br>
ffmpeg.avcodec_send_frame(_pCodecContext, <br>
&frame).ThrowExceptionIfError();<br>
//ffmpeg.av_buffer_unref(&MetaDataBuffer);<br>
}<br>
<br>
62 MB leaked per 100000 frames:<br>
fixed (byte* pMessageData = message)<br>
{<br>
AVBufferRef* MetaDataBuffer = <br>
ffmpeg.av_buffer_alloc((ulong)message.Length);<br>
System.Buffer.MemoryCopy(pMessageData, MetaDataBuffer->data, <br>
(ulong)message.Length, (ulong)message.Length);<br>
//AVFrameSideData* sideData = <br>
ffmpeg.av_frame_new_side_data_from_buf(&frame, <br>
AVFrameSideDataType.AV_FRAME_DATA_SEI_UNREGISTERED, MetaDataBuffer);<br>
ffmpeg.avcodec_send_frame(_pCodecContext, <br>
&frame).ThrowExceptionIfError();<br>
//ffmpeg.av_buffer_unref(&MetaDataBuffer);<br>
}<br>
<br>
0 MB memory leaked per 100000 frames:<br>
fixed (byte* pMessageData = message)<br>
{<br>
AVBufferRef* MetaDataBuffer = <br>
ffmpeg.av_buffer_alloc((ulong)message.Length);<br>
System.Buffer.MemoryCopy(pMessageData, MetaDataBuffer->data, <br>
(ulong)message.Length, (ulong)message.Length);<br>
//AVFrameSideData* sideData = <br>
ffmpeg.av_frame_new_side_data_from_buf(&frame, <br>
AVFrameSideDataType.AV_FRAME_DATA_SEI_UNREGISTERED, MetaDataBuffer);<br>
ffmpeg.avcodec_send_frame(_pCodecContext, <br>
&frame).ThrowExceptionIfError();<br>
ffmpeg.av_buffer_unref(&MetaDataBuffer);<br>
}<br>
<br>
24.5 MB leaked per 100000 frames:<br>
fixed (byte* pMessageData = message)<br>
{<br>
AVBufferRef* MetaDataBuffer = <br>
ffmpeg.av_buffer_alloc((ulong)message.Length);<br>
System.Buffer.MemoryCopy(pMessageData, MetaDataBuffer->data, <br>
(ulong)message.Length, (ulong)message.Length);<br>
AVFrameSideData* sideData = <br>
ffmpeg.av_frame_new_side_data_from_buf(&frame, <br>
AVFrameSideDataType.AV_FRAME_DATA_SEI_UNREGISTERED, MetaDataBuffer);<br>
ffmpeg.avcodec_send_frame(_pCodecContext, <br>
&frame).ThrowExceptionIfError();<br>
ffmpeg.av_buffer_unref(&MetaDataBuffer);<br>
}<br>
<br>
Best regards,<br>
<br>
Vlad<br>
<br>
On 3/2/2023 09:35, Yurii Monakov wrote:<br>
> av_buffer_alloc allocates buffer of given length (it’s data pointer is <br>
> not null). And after that you replace that pointer to with your own <br>
> pointer. So, the first allocation get definitely lost.<br>
> You should copy pMessageData to MetaDataBuffer->data (and free <br>
> pMessageData manually) or use av_buffer_create function.<br>
><br>
> Yurii<br>
><br>
> Ср, 1 марта 2023 г. в 06:55, Wladislav Artsimovich <ffmpeg@frost.kiwi>:<br>
><br>
> Dear FFmpeg and libav users,<br>
><br>
> I am using FFmpeg.AutoGen in my C# Program to write out frames<br>
> encoded<br>
> as a h.264 stream and inject per-frame metadata with an<br>
> unregistered SEI<br>
> Message. It works great, but I have a memory leak, which I don't know<br>
> how to address. Source file attached.<br>
><br>
> Culprit is<br>
> ```C#<br>
> fixed (byte* pMessageData = message)<br>
> {<br>
> AVBufferRef* MetaDataBuffer =<br>
> ffmpeg.av_buffer_alloc((ulong)message.Length);<br>
> MetaDataBuffer->data = pMessageData;<br>
> AVFrameSideData* sideData =<br>
> ffmpeg.av_frame_new_side_data_from_buf(&frame,<br>
> AVFrameSideDataType.AV_FRAME_DATA_SEI_UNREGISTERED, MetaDataBuffer);<br>
> }<br>
> ```<br>
> I create an AVBuffer, as required by<br>
> av_frame_new_side_data_from_buf().<br>
> But I cannot free it, resulting in a memory leak. I went through<br>
> all of<br>
> <a href="https://ffmpeg.org/doxygen/trunk/group__lavu__buffer.html" rel="noreferrer" target="_blank">https://ffmpeg.org/doxygen/trunk/group__lavu__buffer.html</a> and<br>
> tried out<br>
> different av_freep() av_free(), av_buffer_unref() functions, changing<br>
> when to free etc. When I think I perform the free correctly, nothing<br>
> happens. No error, no freeing just nothing. Clearly I misunderstand<br>
> something.<br>
> To add insult to injury, the Visual Studio profiler cannot look<br>
> inside<br>
> the unmanaged memory of libav and reports, that the heap is fine<br>
> and not<br>
> growing, see attached screenshot.<br>
><br>
> How and when can I free this memory created allocated by<br>
> av_buffer_alloc() in the attached source file?<br>
><br>
> I asked the same question in the FFmpeg.AutoGen Questions Repo. Some<br>
> more context there:<br>
> <a href="https://github.com/Ruslan-B/FFmpeg.AutoGen.Questions/issues/36" rel="noreferrer" target="_blank">https://github.com/Ruslan-B/FFmpeg.AutoGen.Questions/issues/36</a><br>
><br>
> Best regards,<br>
><br>
> Vlad<br>
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</blockquote></div>
</div></div>