[Libav-user] AVUtil memory leaks

[Tomislav Timic]

This is how I am opening output

AVFormatContext *fmtCtx = nullptr;
if (avformat_alloc_output_context2(&fmtCtx, nullptr,
output.format.c_str(), output.url.c_str()) < 0)
{
    LOG(INFO) << "Failed to open mux format context";
    release();
    return false;
}


if (muxFormatCtx.at(0)->oformat->flags & AVFMT_GLOBALHEADER)
{
    muxFormatCtx.at(0)->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
}

if (!(muxFormatCtx.at(0)->oformat->flags & AVFMT_NOFILE))
{
    if (avio_open(&muxFormatCtx.at(0)->pb,
                  pipeline->getOutputs().outputs[0].url.c_str(),
                  AVIO_FLAG_WRITE) < 0)
    {
        LOG(INFO) << util::string::StringFmtUtil::format("Could not
open output format = %s",

pipeline->getOutputs().outputs[0].url.c_str());
        release();
        return false;
    }
}

if (avformat_write_header(muxFormatCtx.at(0), nullptr) < 0)
{
    LOG(ERROR) << "Error occurred while opening mux format";
    release();
    return false;
}


And this is how i free it

for (auto formatCtx: muxFormatCtx)
{
    if (formatCtx != nullptr)
    {
        av_write_trailer(formatCtx);

        if (!(formatCtx->oformat->flags & AVFMT_NOFILE))
        {
            avio_closep(&formatCtx->pb);
        }

        avformat_free_context(formatCtx);
        formatCtx = nullptr;
    }
}
muxFormatCtx.clear();



On Mon, May 12, 2025 at 11:20 AM Jaka Bac <jakabac at gmail.com> wrote:

> On Mon, 12 May 2025 at 11:02, Tomislav Timic <tomislavtimic98 at gmail.com>
> wrote:
>
>> I was observing my application that is doing transcoding of mpegts over
>> udp and I noticed that constantly after each create of transcoder pipeline
>> and delete of pipeline i get small leaks from avutil.
>> [image: Screenshot 2025-05-12 at 11.00.07.png]
>> This is how i release input format context
>>
>> if (formatCtx != nullptr)
>> {
>>     avformat_close_input(&formatCtx);
>>     avformat_free_context(formatCtx);
>>     formatCtx = nullptr;
>> }
>>
>> This is how i release decoder
>>
>> if (frame != nullptr)
>> {
>>     av_frame_free(&frame);
>>     frame = nullptr;
>> }
>>
>> if (videoCodecCtx != nullptr)
>> {
>>     if (videoCodecCtx->codec != nullptr &&
>>         videoCodecCtx->codec->capabilities & AV_CODEC_CAP_ENCODER_FLUSH)
>>     {
>>         avcodec_flush_buffers(videoCodecCtx);
>>     }
>>     avcodec_free_context(&videoCodecCtx);
>>     videoCodecCtx = nullptr;
>> }
>>
>> if (audioCodecCtx != nullptr)
>> {
>>     if (audioCodecCtx->codec != nullptr &&
>>         audioCodecCtx->codec->capabilities & AV_CODEC_CAP_ENCODER_FLUSH)
>>     {
>>         avcodec_flush_buffers(audioCodecCtx);
>>     }
>>     avcodec_free_context(&audioCodecCtx);
>>     audioCodecCtx = nullptr;
>> }
>>
>> and this is how i release encoder and muxer
>>
>> if (codecCtx != nullptr)
>> {
>>     avcodec_free_context(&codecCtx);
>>     codecCtx = nullptr;
>> }
>>
>> if (encodePkt != nullptr)
>> {
>>     av_packet_free(&encodePkt);
>>     encodePkt = nullptr;
>> }
>>
>> if (packet != nullptr)
>> {
>>     av_packet_free(&packet);
>>     packet = nullptr;
>> }
>>
>> for (auto formatCtx: muxFormatCtx)
>> {
>>     if (formatCtx != nullptr)
>>     {
>>         av_write_trailer(formatCtx);
>>
>>         if (!(formatCtx->oformat->flags & AVFMT_NOFILE))
>>         {
>>             avio_closep(&formatCtx->pb);
>>         }
>>
>>         avformat_free_context(formatCtx);
>>         formatCtx = nullptr;
>>     }
>> }
>>
>>
> There is no need to do both avformat_close_input() and then
> avformat_free_context() since avformat_close_input will also free the
> context.
> avformat_free_context() in your case finds out that it got a null pointer
> and doesn't do anything.
>
> As for your leak, how are you opening the output? Maybe you are missing an
> avio_closep() ?
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