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[79.124.17.100]) by mx.google.com with ESMTP id n7si18580526edw.348.2021.12.13.18.12.28; Mon, 13 Dec 2021 18:12:29 -0800 (PST) Received-SPF: pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) client-ip=79.124.17.100; Authentication-Results: mx.google.com; dkim=neutral (body hash did not verify) header.i=@gmail.com header.s=20210112 header.b=Cw0tANXg; spf=pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) smtp.mailfrom=ffmpeg-devel-bounces@ffmpeg.org; dmarc=fail (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id 1122668A853; Tue, 14 Dec 2021 04:12:25 +0200 (EET) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from mail-ot1-f46.google.com (mail-ot1-f46.google.com [209.85.210.46]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 2913E68A2F6 for ; Tue, 14 Dec 2021 04:12:18 +0200 (EET) Received: by mail-ot1-f46.google.com with SMTP id a23-20020a9d4717000000b0056c15d6d0caso19416264otf.12 for ; Mon, 13 Dec 2021 18:12:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:subject:date:message-id:mime-version :content-transfer-encoding; bh=MKvWWK0NlpJoylYm70+75RHGy4CQ8wk2X50TJLqKCBM=; b=Cw0tANXgtJyq1HVSbYcRlM4L3Sw0IPT3wYt9tYhXmkse79yHDUPg2ohE6txETeeLyl kw7o0ne72R/mKqHcQn7gWVnsMLsUHIfPr0HYAGREUoYnbQymdRQtEIO7llIwohLqzWw9 pEt6dsYOGJO42vzZ4rfSQTmAY4T7KhHKm+acayihHDUWQc+NIvngixDy0g8LVyrCEgfI DNqjsHYyOLMNzef6x46wX9Hken0u2D4srSekBjLeFdw1Y0W+YXGQuoWK9aUYQqv5DGN4 qt/T72d6AvZilFjpKl6RDuxkkIDVDIZUGkSRNsWKkNfFPwP2SojqFeapFoZrWIkg9Iva RKTA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:subject:date:message-id:mime-version :content-transfer-encoding; bh=MKvWWK0NlpJoylYm70+75RHGy4CQ8wk2X50TJLqKCBM=; b=e1m73p91cILO8tCOe3FMtlWGE7OaNUp0voECclqWO1v32WjvMu6b2lyaJQcpv28bFt Pbxz17RI8xFbjOhX/uVI8u7tSYNMGypLhh1VCo0gdQx9mGzZnzB4YWmnZ7tqAYcHVzfG kea/Y3Uj61pRKHpxqhIxUxeZTIs8SjROrU2ukZUEIK6uDAIhXXSj53OzwAW19tTpDohS 9NZLbt7P0CMIqLWZfmAi7vY9U5CZpjLMyqk2G8RgJ3pYO61fQBDzN5af7QTB9f+0d9po 16hYQJWliLp6TNrKETU6M6wl2MijMHy+iGBwxxkDlrXGbKooNGNIw/LjZ3e5+XlB4xgC 2hCA== X-Gm-Message-State: AOAM533XKbmXP+db5ZgbaxSFn5i5U9coPjsLeIRaIB5IFSR/L20Pkw7w D0H5kgRvEj6Ba/7pOVhSn5JNk1YL5Wg= X-Received: by 2002:a9d:62d9:: with SMTP id z25mr1867920otk.330.1639447936230; Mon, 13 Dec 2021 18:12:16 -0800 (PST) Received: from ubuntu-vbuilder.localdomain ([2600:1700:4830:3f7f:20c:29ff:fe04:f136]) by smtp.gmail.com with ESMTPSA id j13sm2962539oil.42.2021.12.13.18.12.15 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Dec 2021 18:12:15 -0800 (PST) From: Cameron Gutman To: ffmpeg-devel@ffmpeg.org Date: Tue, 14 Dec 2021 02:12:15 +0000 Message-Id: <20211214021215.456493-1-aicommander@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH] avcodec/v4l2_m2m_dec: dequeue frame if input isn't ready X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" X-TUID: Gkb+jcVpRNV1 The V4L2M2M API operates asynchronously, so multiple packets can be enqueued before getting a batch of frames back. Since it was only possible to receive a frame by submitting another packet, there wasn't a way to drain those excess output frames from when avcodec_receive_frame() returned AVERROR(EAGAIN). In my testing, this change reduced decode latency of a real-time 60 FPS H.264 stream by approximately 10x (200ms -> 20ms) on a Raspberry Pi 4. Signed-off-by: Cameron Gutman --- libavcodec/v4l2_m2m_dec.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c index 224eb3d5e7..b0c3d30ac8 100644 --- a/libavcodec/v4l2_m2m_dec.c +++ b/libavcodec/v4l2_m2m_dec.c @@ -142,8 +142,12 @@ static int v4l2_receive_frame(AVCodecContext *avctx, AVFrame *frame) if (!s->buf_pkt.size) { ret = ff_decode_get_packet(avctx, &s->buf_pkt); - if (ret < 0 && ret != AVERROR_EOF) - return ret; + if (ret < 0) { + if (ret == AVERROR(EAGAIN)) + return ff_v4l2_context_dequeue_frame(capture, frame, 0); + else if (ret != AVERROR_EOF) + return ret; + } } if (s->draining)