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IntentVizor: Towards Generic Query Guided Interactive Video Summarization

Guande Wu   Jianzhe Lin 11footnotemark: 1   Claudio T. Silva
New York University
{guandewu, jianzhelin, csilva}@nyu.edu
equal contribution
Abstract

The target of automatic video summarization is to create a short skim of the original long video while preserving the major content/events. There is a growing interest in the integration of user queries into video summarization or query-driven video summarization. This video summarization method predicts a concise synopsis of the original video based on the user query, which is commonly represented by the input text. However, two inherent problems exist in this query-driven way. First, the text query might not be enough to describe the exact and diverse needs of the user. Second, the user cannot edit once the summaries are produced, while we assume the needs of the user should be subtle and need to be adjusted interactively. To solve these two problems, we propose IntentVizor, an interactive video summarization framework guided by generic multi-modality queries. The input query that describes the user’s needs are not limited to text but also the video snippets. We further represent these multi-modality finer-grained queries as user ‘intent’, which is interpretable, interactable, editable, and can better quantify the user’s needs. In this paper, we use a set of the proposed intents to represent the user query and design a new interactive visual analytic interface. Users can interactively control and adjust these mixed-initiative intents to obtain a more satisfying summary through the interface. Also, to improve the summarization quality via video understanding, a novel Granularity-Scalable Ego-Graph Convolutional Networks (GSE-GCN) is proposed. We conduct our experiments on two benchmark datasets. Comparisons with the state-of-the-art methods verify the effectiveness of the proposed framework. Code and dataset are available at https://github.com/jnzs1836/intent-vizor.

1 Introduction

Refer to caption
Figure 1: Illustration of our IntentVizor framework. We take query “Table” as an example. Generic queries, including text/video snippets related to “Table” are inputs of the model. The intent module transforms these queries into a probability distribution over the basis intents, followed by the summary module, which generates a video summary by combing the basis intents and their probability values. As the user can find the underlying visual semantic meaning of each basis intents (e.g., in the figure, basis intent #1: the dining table; #2: the working table), they can adjust the distribution of these basis intents through our proposed interface (Fig. 4) to satisfy their needs, and the final generated summaries can be updated accordingly/iteratively.

With the online explosive video content, an increasing need has been identified for automatic video summarization in recent years. Traditional video summarization methods usually generate concise/representative summary that contains the entities and events with high priority from the video and with low repetition and redundancy using unsupervised [15, 20, 5, 25, 38, 45, 16], supervised [26, 51, 44, 47, 7, 27, 48] and reinforcement learning ways[2, 49]. However, such a summary cannot satisfy the needs of users and be of low practical value. As the elongated video, especially when captured in the realistic scenario, may cover a wide range of topics, only fractional content of specific topics will meet the user’s needs. Based on this observation, the user query-driven summarization model, which considers the user’s preference, has gradually attracted researchers’ attention.

The basic idea for query-driven summarization is to use the text query to guide the generation of video summaries. A popular dataset for this query-driven summarization was the textual query dataset, proposed by Sharghi et al. [29]. The summarization model proposed in the paper was trained to predict a subset of the video shots (5 seconds per shot) closely related to the textual query. For the follow-up works, the attention mechanism [36, 35, 22] and generative adversarial networks[46] based summarization models are also introduced to achieve better summarization performance. However, the performance of these models was still not satisfying as the textual query is not enough to represent the users’ preferences. To be more specific, first, the user cannot express their detailed needs with few fixed input textual queries at the very beginning of summarization. They may have multiple needs and want to adjust the priority of different needs. Second, the textual query can be ambiguous. People can have different understandings of a word in the communication, let alone the model trained on a fixed word dictionary. Therefore, the model should be interactive to loop users into the summarization, and other query formats (e.g., visual query) should be considered to better represent the user preference with lower ambiguity.

To propose a generic model for queries from different modalities and allow users to interact during the summarization process, in this paper, we propose a novel framework named as IntentVizor. We borrow the concept Intent from the Information Retrieval (IR) community to define the users’ need, independent of the query modalities[17, 43, 3]. However, our intent differs from the traditional definition in IR with different representation and extraction: (1) We represent the intent by an adjustable distribution over the basis intents rather than the pre-defined categories[3] , taxonomies[40, 4] or in a distributed representation space[41, 12]; The basis intents are defined as the learned and basic components of the user’s needs. Compared with the traditional definitions[3, 40, 4, 41, 12], our method enables interactive manipulation, satisfying the user’s diverse and subtle needs. (2) We extract a unified intent from the queries of different modalities instead of only the textual query to avoid the ambiguity problem as mentioned before.

The intentVizor framework consists of two modules, i.e., the intent module for extracting the intent from the query and the summary module for summarizing the video with the intent. To effectively correlate the video features with the generic query/intent in the two modules, we design a flexible network structure named Granularity-Scalable Ego-Graph Convolutional Network (GSE-GCN). This GSE-GCN will work as a shared backbone for both the summary module and the intent module. Besides this backbone, the two modules each has an intent head and a summary head separately.

To sum up, we structure our contributions as follows:

  • To the best of our knowledge, our IntentVizor framework is the first attempt to introduce generic queries to better satisfy the user’s diverse needs. We also propose a novel dataset for the visual-query-guided video summarization based on UTE videos.

  • We formulate the video summarization as an interactive process, where the user can fine-tune its intent iteratively with our proposed novel interface.

  • We propose a novel GSE-GCN structure to effectively correlate the generic queries of multi-modalities with the input video.

2 Related Works

2.1 Summarizing Video with User Intent

Integrating the user query in video summarization has long been a hot topic. Previous approaches often represent the query by the textual concepts. Sharghi et al. built the first query-focused video summarization dataset based on the UTE video dataset and proposed an evaluation protocol based on the shot-level semantic tags, which became the standard protocol for the research community [29]. Zhang et al. proposed a generative adversarial network (GAN) to address the problem [46]. Xiao et al. defined the task as a shot-query similarity problem and proposed a convolution-based network to capture the local and global information[36]. We also calculate the distance-based similarity between the video shots and user intent. Jiang et al. employed a multilevel self-attention module and a variational autoencoder (VAE) to add user-oriented diversity and stochastic factors[13]. Although their work also paid attention to the user intent, they did not allow the interactive adjustment of the intent. Instead, recent works gradually noticed the importance of the user feedback and user interaction [14, 6]. However, these works still lack a flexible method for the user to control the interaction process. To solve this problem, we achieved this interaction through intent (the controllable variable for user) adjusting in this paper.

2.2 Graph Convolutional Networks for Videos

Graph convolutional networks have been widely applied on various video analysis tasks. The approaches can be roughly divided into two categories based on the graph type, i.e., spatio-temporal graph and snippet graph. Spatio-Temporal graph views the video as a graph of region proposals or objects in the spatio-temporal domain. Liu et al. represented the video as a space-time region graph and applied a GCN to perform the action recognition [33]. Yan et al. modeled the dynamic body joints as a spatio-temporal graph to estimate the human pose [39]. Similar approaches were also employed in a wide range of tasks including, action recognition[21, 32, 10], human re-identification[19], gaze prediction[8], and video captioning[24]. Unlike the above works, the snippet graph correlated the snippets (‘snippets’ are ‘segments’ in our paper, as mentioned before) by their semantic and temporal relationships. Zeng et al. built a graph of the temporal 1-D proposals to perform the temporal action localization[42]. Xu et al. constructed a snippet graph and designed an efficient edge convolution method to detect the temporal action[37]. We borrowed their edge convolution operation when we introduced a hybrid graph with the user intent to align the video segments and user intent.

3 IntentVizor Framework

Our IntentVizor framework targets at (1) interactive control over the video summarization process; (2) support of the generic multi-modality query. This section first shows that the two requirements can be satisfied by modelling the multi-modality queries as a unified and interactive user intent. Then, we will describe GSE-GCN, which is designed to better deal with multi-modality queries.

Refer to caption
Figure 2: GSE-GCN exploits two notions i.e., GS-Pathway and Ego-Graph. The input video will be processed by two convolutional networks to produce two segment-level feature sequence of coarse and fine granularity. Then, each sequence will be processed to generate a Ego-Graph, where the intent/query vertex is an ego-vertex with all the video segments are connected. After feeding the graph into GCN, the two pathways will be produce the corresponding segment-level features. Intent Head pools the segment features into a distributed representation, which will be processed by a MLP with softmax to produce the intent probability. Summary Head exploits the local-GCN module to produce the shot-level features, which will be used to predict the shot selection probability.

.

3.1 Unified and Interactive User Intent

3.1.1 Problem Setting

We introduce a novel problem setting with our proposed unified and interactive intent. The canonical setting for query-focused video summarization is to output a representative and concise subset of video shots based on the inputting video 𝒗\boldsymbol{v} of TT shots and text query qtq_{t}. We re-define the task by generalizing the text query qtq_{t} into the generic query qq. Then, we propose to predict not only a final video summary, but also a unified and interactive user intent ζ\zeta for the multi-modality queries. ζ\zeta can be learned implicitly like a latent variable. We assume that there are a set of basis intents as Z={ζ1,ζ2,,ζk}Z=\{\zeta_{1},\zeta_{2},...,\zeta_{k}\} and the user intent ζ\zeta is chosen from the basis intents according to a categorical distribution conditioned on the query qq as ζp(ζ|q,v)\zeta\sim p(\zeta|q,v). Given the user query qq, the distribution p(ζ|q,v)p(\zeta|q,v) is parameterized by the probability vector of basis intents, 𝒑(𝜻)=[p(ζ1|q,𝒗),p(ζ2|q,𝒗),,p(ζk|q,𝒗)]T\boldsymbol{p(\zeta)}=[p(\zeta_{1}|q,\boldsymbol{v}),p(\zeta_{2}|q,\boldsymbol{v}),...,p(\zeta_{k}|q,\boldsymbol{v})]^{T}.

In practice, the query can be either textual, visual, or other formats. In this work, we only implement the models for textual and visual queries. Following the previous works[29], we represent the text query by two text concepts as qt={c1,c2}q_{t}=\{c_{1},c_{2}\}, where c1c_{1}, c2c_{2} are two concepts. By comparison, we represent the visual query by a set of representative shots in the original video as qv={u1,u2,,uP}q_{v}=\{{u}_{1},u_{2},...,u_{P}\} where PP is a constant number.

Then, for each shot ss, we denote ηs{True,False}\eta_{s}\in\{True,False\} as whether ss should be selected in the summarization. We assume that ηs\eta_{s} is sampled from a Bernoulli distribution conditioned on the intent as

p(ηs)=p(ηs|ζ,𝒗).p(\eta_{s})=p(\eta_{s}|\zeta,\boldsymbol{v}). (1)

Finally, we can condition the shot selection probability p(ηs)p(\eta_{s}) on the user query as

p(ηs|q)=Σi=1ikp(ζi|q,𝒗)p(ηs|ζi,𝒗).p(\eta_{s}|q)=\Sigma_{i=1}^{i\leq k}p(\zeta_{i}|q,\boldsymbol{v})*p(\eta_{s}|\zeta_{i},\boldsymbol{v}). (2)

Instead of the deterministic intent ζ\zeta, we characterize the user’s needs by the distribution p(ζ|q,𝒗)p(\zeta|q,\boldsymbol{v}), which weights different basis intents as Equation 2 shows. Such a notion follows the perspective of Bayesianism as the latent variable (intent) is a random variable instead of a deterministic value. The user can iteratively adjust the probability vector 𝒑(𝜻)\boldsymbol{p(\zeta)} to fine-tune its intent.

Since the shot selection probability is often viewed as a summarization score when η=True\eta=True, we use the shot score and selection probability interchangeably in this paper. To implement Equation 1, and 2, we design two modules 𝒑(ζ|q)=g(q,𝒗:θg)\boldsymbol{p}(\zeta|q)=g(q,\boldsymbol{v}:\theta_{g}) (intent module) and p(ηs|ζ)=h(ζ,𝒗:θh)p(\eta_{s}|\zeta)=h(\zeta,\boldsymbol{v}:\theta_{h}) (summary module), where θg\theta_{g} and θh\theta_{h} are the parameters of gg and hh

p(ηs|q,𝒗)=Σi=1ikgi(q,𝒗:θg)h(ζi,𝒗:θh).p(\eta_{s}|q,\boldsymbol{v})=\Sigma_{i=1}^{i\leq k}g_{i}(q,\boldsymbol{v}:\theta_{g})*h(\zeta_{i},\boldsymbol{v}:\theta_{h}). (3)

Given the ground truth labels, we can optimize the parameters θg,θh\theta_{g},\theta_{h} of our modules by the BCE Loss as

BCE(θg,θh)=Σt=1tTlog(p(yt|q,𝒗)),\mathscr{L}_{BCE}(\theta_{g},\theta_{h})=\Sigma_{t=1}^{t\leq T}log(p(y_{t}|q,\boldsymbol{v})), (4)

where yty_{t} is the ground truth label for the ttht^{th} shot.

3.1.2 Non-Linear Activation

The Equation 3 strictly follows the selection probability’s theoretical definition in Equation 2. However, it restricts the capacity of the intent module because the resulting probability is simply the linear combination of h(ζi,𝒗)gi(q,𝒗)h(\zeta_{i},\boldsymbol{v})*g_{i}(q,\boldsymbol{v}). To address the issue, we trade off the strictness for better performance by adding a non-linearity layer on every basis intent score. Specifically, we employ shifted ReLU[1] as the non-linearity activation.

p(ηs|q)=Σi=1ikReLU(gi(q,𝒗)h(ζi,𝒗)δ),p(\eta_{s}|q)=\Sigma_{i=1}^{i\leq k}ReLU(g_{i}(q,\boldsymbol{v})*h(\zeta_{i},\boldsymbol{v})-\delta), (5)

where δ\delta refers to the threshold value for the shifted ReLU.

3.2 GSE-GCN: Granularity-Scalable Ego-Graph Convolutional Networks

As the shared backbone of intent module gg and summary module hh, the GSE-GCN exploits two newly proposed components, i.e., Granularity-Scalable Pathways (GS-Pathways) and Ego-Graph Convolutional Network (E-GCN), to better deal with the temporal multi-granularity and sparsity of correlation respectively.

3.2.1 Granularity-Scalable Pathways (GS-Pathways)

Layer Coarse Pathway Fine Pathway
Kernel Stride Channel Output Size Kernel Stride Channel Output Size
Conv1 5 8 1024 [L//8, 1024] 5 1 256 [L//2, 256]
MaxPool1 2 1 1024 [L//8, 1024] 2 2 256 [L//2, 256]
Conv2 5 1 1024 [L//8, 1024] 5 1 256 [L//2, 256]
MaxPool2 3 2 1024 [L//16, 1024] 2 2 256 [L//4, 256]
Table 1: The hyperparameter setting of the granularity-scalable pathways. LL refers to the length of the original video.
Refer to caption
Figure 3: The eating action (Clip A) with a longer length should be processed with the coarser-grained features by the coarse pathway. By comparison, the jumping event (Clip B) with far faster movement should be processed with the finer-grained features.

Models with the constant temporal granularity may fall short in aligning the video events/actions of multi-granularity with the user query/intent. We have shown in Figure 3 that the actions of different temporal lengths and movement speeds should be processed with the features of different temporal granularity. The issue raises the necessity of a granularity-scalable model. To realize it, we propose a flexible structure with two pathways of different granularity. The idea is similar with [9] technically while being motivated by different concerns. For each pathway, we aggregate shot-level features into segment-level features (a segment spans 4 and 16 shots with the fine and coarse pathways, respectively) by a convolutional network. We list the hyper-parameters in Table 1. The produced segment-level features are fed into our E-GCN described below to align with the query/intent.

3.2.2 Ego-Graph Convolutional Networks

The correlations between the different video segments and query/intent can be relatively sparse given a long video. For example, if the user queries “walking”, there can be only a fraction of video content correlated with walking people. Besides, the query-related video content can also have a sparse relationship with other video segments, especially those having a long temporal distance. Thus, correlating all the video segments (e.g., transformer-based models) can be time-inefficient and space-inefficient. We propose to exploit the notion of dynamic edge convolution [34] and construct a graph 𝒢=(𝒱,)\mathscr{G}=(\mathscr{V},\mathscr{E}) by connecting the video segments and query/intent dynamically. The graph’s vertices 𝒱\mathscr{V} comprises of video segments extracted from the above GS-Pathways and the query/intent. To dynamically model the correlations between the video segments and the user intent, we connect them with the edge set \mathscr{E} consisting of three types of edges, i.e., intent edge i\mathscr{E}_{i}, semantic edge s\mathscr{E}_{s}, and temporal edge t\mathscr{E}_{t}.

Intent Edge connects the segment vertices with the centric intent vertex, which is why we call the graph as Ego-Graph. We map the intent embedding and segment feature into a mutual latent space dynamically by two MLPs. Then we can derive the intent-segment edge set z\mathscr{E}_{z} as,

z={(w,wt),wt𝒱T},\mathscr{E}_{z}=\{(w^{\prime},w_{t}),w_{t}\in\mathscr{V}_{T}\}, (6)

where 𝒱T\mathscr{V}_{T} refers to the vertex set of the video segments and ww^{\prime} refers to the mapped query/intent vertex.

Semantic Edge connects the video segments with the correlated semantics. Motivated the sparsity of correlation, we follow [37] and connect the top-k related vertices for each video segment vertex in 𝒱T\mathscr{V}_{T}.

s={(wt,wnt(k))|t=1,2,,T;k=1,2,,K},\mathscr{E}_{s}=\{(w_{t},w_{n_{t}(k)})|t=1,2,...,T;k=1,2,...,K\}, (7)

where wnt(k)w_{n_{t}(k)} is the kthk^{th} nearest neighbor of the vertex wtw_{t} in the feature space and KK is a constant number.

Temporal Edge connects the edges temporally adjacent. Each vertex has a forward edge to the next vertex and a backward edge to the last vertex except the two ends of the segment sequence. We represent the two sets of edges as:

tf={(wt,wt+1|t=1,2,,T1},\mathscr{E}^{f}_{t}=\{(w_{t},w_{t+1}|t=1,2,...,T-1\}, (8)
tb={(wt,wt1|t=2,3,,T},\mathscr{E}^{b}_{t}=\{(w_{t},w_{t-1}|t=2,3,...,T\}, (9)

where tf\mathscr{E}^{f}_{t} includes the forward temporal edges, tb\mathscr{E}^{b}_{t} includes the backward temporal edges and t=tbtb\mathscr{E}_{t}=\mathscr{E}^{b}_{t}\cup\mathscr{E}^{b}_{t}.

Edge Convolution After obtaining the graph, We apply edge convolution as our graph convolution operation[34]. Following Xu et al.[37], We employ the convolution operation to perform the efficient edge convolution on the obtained graph.

3.2.3 Local Graph for Shot-Level Features

The output features of edge convolution are at segment-level. To reconstruct the shot feature sequence from the segment features, We build the local Ego-Graph for each segment. The graph consists of one segment feature vertex connected with the all spanned shot vertices. We also add the semantic and temporal edges to the graph. After applying edge convolution on the constructed graph, we can obtain a shot-level feature sequence.

3.2.4 Implementation of the Modules

Both intent and summary modules are implemented based on GSE-GCN with different inputs and outputs. The summary module performs element-wise multiplication on the intent embedding and the Local-GCN-processed shot features to get a similarity vector. Then it exploits an MLP with Sigmoid activation to generate the selection probability of shots. By comparison, the intent module exploits an MLP head with Softmax to generate the intent distribution. Since the intent module is designed for the queries of different modalities, there is a slight difference between the visual-query and textual-query. The intent module for textual query strictly follows the GSE-GCN structure, while the intent module for the visual query models the query shots as individual vertices instead of one merged vertex.

4 Experiments

Refer to caption
Figure 4: Prototype Overview. A: Summary View presents two temporal bar charts, which shows the overall scores and the summarized shots. The bottom bar chart shows the overview of all the shots, while the top bar chart zooms into the detail decided by the brush in the bottom chart. B: Intent View list all the basis intents with their probability, shot scores, and representative samples. The samples are selected with the highest score. C: Preview View plays a GIF of the user-hovering shot. In this case, the user hovers on the highlighted shot in intent #12, which includes a room scenario. D: Query View allows the user to change the query and makes the model rerun. E Evaluation View shows the quantitative result of the summary.
Video-1 Video-2 Video-3 Video-4 Avg.
Method Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1
QC-DPP [29] 49.86 53.38 48.68 33.71 62.09 41.66 55.16 29.24 36.51 21.39 63.12 29.96 40.03 60.25 44.19
CHAN [36] 54.73 46.57 49.14 45.92 50.26 46.53 59.75 64.53 58.65 25.23 51.16 33.42 46.40 53.13 46.94
HVN [13] 52.55 52.91 51.45 38.66 62.70 47.49 60.28 62.58 61.08 26.27 54.21 35.47 44.57 58.10 48.87
QSAN [35] 48.41 52.34 48.52 46.51 51.36 46.64 56.78 61.14 56.93 30.54 46.90 34.25 45.56 52.94 46.59
Nalla et al. [23] 54.58 52.51 50.96 48.12 52.15 48.28 58.48 61.66 58.41 37.40 43.90 39.18 49.64 52.55 49.20
Ours 62.19 45.23 51.27 50.43 57.81 53.48 73.45 53.56 61.58 28.24 56.47 37.25 53.58 53.27 50.90
Table 2: Textual Query Dataset: Comparison with the previous state-of-the-art approaches.
Video-1 Video-2 Video-3 Video-4 Avg.
Method Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1 Pre. Rec. F-1
Linear Baseline 59.24 45.33 49.75 21.49 26.71 23.62 56.09 44.42 49.22 14.44 33.1 19.77 37.82 37.39 35.59
Attention Baseline 45.01 33.96 37.71 38.86 48.01 41.09 57.7 48.75 50.66 18.00 41.5 24.75 39.89 43.06 38.55
Ours 58.17 44.91 49.43 42.52 52.69 46.64 65.45 51.92 57.49 21.15 49.23 29.19 46.82 49.69 45.69
Table 3: Visual Query Dataset: Comparison with the baselines.

4.1 Implementation Detail

We exploit Pytorch [28] to implement our model on an NVIDIA RTX 8000. We have 20 basis intents, each represented by a 128-D embedding vector. For the summary module, we employ a 3-layer GCN and a 3-layer MLP after the GCN layers. We set the number of GCN layers and MLP layers as 2 and 3 for the intent module. Models are trained by an Adam optimizer with a base learning rate of 1e-4. We employ a warm-up strategy [11] to linearly increase the learning rate from 0 to the base learning rate in 10 epochs. After that, we reduce the learning rate to one-tenth of the previous value every twenty epochs.

4.2 Experiment Setting

4.2.1 Text Query Dataset

We conduct our text-query experiments on the query-driven video summarization dataset [29]. The dataset includes the four videos in UT Egocentric(UTE) dataset[18]. Each of the videos (3-5 hours) is captured in daily life scenarios. Each query in the dataset is represented by two concepts among the total 48 concepts.

4.2.2 Visual Query Dataset and Dataset Baselines

We build our visual-query dataset based on the text-query dataset. For each annotated summarization, we employ the eigenvector centrality as the criteria to pick the most representative shots as the query shots. Detailed examples and descriptions can be found in the supplementary materials. As the visual query dataset is newly introduced and no previous work exists, we compare our approach with two baselines, i.e., linear prediction and attentional query model, which can be founded in the supplementary.

4.2.3 Evaluation Protocol

To compare with the previous approaches fairly, we employ the semantic evaluation protocol proposed by Sharghi et al.[29]. This protocol is based on the semantic similarity between the machine-generated and the ground-truth video shots. The similarity is generated through finding the maximum weight matching of the bipartite graph computed based on the semantic interception-over-union (IOU). The summed weights of the matched shot pairs are used to compute precision, recall, and F-1 measure. Note that for the visual query dataset, we mask out the query shots in the evaluation stage. To evaluate the interactive intent, which involves the human subjectivity, we develop a prototype and propose a case study in qualitative analysis.

4.3 Comparative Analysis

The comparison among our method and SOTA methods for the Textual Query Task can be found in Table 2. We observe that our method achieves the highest F-1 value of 50.90%. The result proves that our method can better identify the correlation between the query and summary. We also present the experimental result on the visual query task in Table 3. We find our method significantly outperforms the baselines by 7%, although the general performance is inferior to the performance on the text query task.

4.4 Ablation Analysis

We evaluate the effects of the proposed methods and find the optimum model setting by an ablation study.

4.4.1 Ego-Graph Convolutional Networks

I.M. S.M. Pre. Rec. F-1
Transformer Transformer 44.82 44.52 42.68
Transformer Ego-GCN 49.00 47.89 46.15
Ego-GCN Transformer 47.09 47.26 44.75
Ego-GCN Ego-GCN 53.58 53.27 50.90
Table 4: Ablation study the proposed Ego-GCN. I.M. refers to the intent module when S.M. refers to the summary module.

Our proposed Ego-GCN approach aligns the video segment features with the query/intent. To validate the effectiveness, we replace Ego-GCN by the transformer-based approach[30, 31, 50] in the intent and summary modules iteratively. The experiment results can be found in Table 4. Our Ego-GCN can advance the model performance when added to either intent or summary module.

4.4.2 Local GCN

Pathway Pre. Rec. F-1
Upsampling 38.04 37.48 35.88
Transpose Conv 47.53 47.41 45.18
Local GCN 53.58 53.27 50.90
Table 5: Ablation study for Local GCN.

We employ Local GCN to recover the shot-level features from the segment-level features. As shown in Figure 5, Local GCN’s performance is superior to bi-cubic upsampling and transpose convolutional layer, which is used in [36].

4.4.3 GS-Pathway

Pathway Pre. Rec. F-1
Shot-Level Feature 47.45 45.38 44.40
Coarse-Granularity 47.40 47.66 45.15
Fine-Granularity 50.18 50.23 47.81
Full-Model 53.58 53.27 50.90
Table 6: Ablation study for the GS-Pathway. The pathway Shot-Level Feature refers to the model that directly applies our Ego-GCN on the shot-level video features.

To validate the effects of our GS-Pathway, we compare our model with three variants with only one fixed pathway. We present the experiment results in Table 6. Our result shows our model surpasses the three variants, verifying the necessity of attending the segment features of multi-granularity.

4.4.4 When to fusion the pathways?

Stage Pre. Rec. F-1
Early 53.58 53.27 50.90
Middle 49.53 48.66 46.66
Late 47.69 47.98 45.47
Table 7: Experiment result on the feature fusion stage.

The features of different pathways can fuse at different stages. To find the optimum of the model, we compare the variants with different fusion strategies, i.e, early, middle, late fusions. The early fusion strategy fusions the features before the dot product shown in Fig. 2. The middle fusion and late fusion happen before and after the MLP, respectively. As can be found in Table 7, fusion at the early stage is the best choice.

4.4.5 Do we need video as input of the intent modules?

Intent Module Pre. Rec. F-1
Video Agnostic 50.06 48.78 47.15
Query Attention 49.26 47.85 46.27
Full Model 53.58 53.27 50.90
Table 8: Experiments on the video inputs in the intent module.

Our intent module use both the query and video as input to predict the user intent. However, the user intent can also solely rely on the user query, as some users might not have time to browse the original videos. Thus, it is necessary to learn if we can remove the video inputs from the intent module and let it infer only based on the user query. To do so, we compare the full model with two variants using a simpler intent module and a video-agnostic intent module. We present the experiment result in Table 8. Though there is a marginal performance decrease, the model with a video-agnostic intent module still outperforms most of the previous state-of-the-art approaches. The result shows it is reasonable to remove the video input for the intent module to promote the model’s generalizability.

4.4.6 Can we transfer the summary module between different datasets?

Training Pre. Rec. F-1
Canonical 46.82 49.69 45.69
Transferring 47.15 51.08 46.40
Table 9: Experiment on visual query task with transfer learning.

To validate the generality of the summary module, we experiment on the visual-query task in the transferring setting. We first train the summary module on the text-query dataset. Then, we reuse this pre-trained summary module and only train the intent module for the visual-query task. The results can be found in Table 9. The experiment result shows that the transferred model surpasses the model trained in the canonical setting, showing that the summary module is interchangeable for the queries of multi-modality.

4.5 Prototype and Qualitative Analysis

We demonstrate the interactivity of our framework with a prototype as shown in Fig. 4. The prototype can also work as qualitative analysis, to prove that our approach can generate the query-related summary with better interpretability. In the figure, we show an example case. The snapshot is taken when the user queries “Food” and “Room” for video-3. Note here we set that the user input is always two queries in our design of the prototype, although the proposed framework can deal with other numbers of queries. The user first brushes on the result view and focuses on the clip where more shots are captured in the summary. Based on the Intent View (B), we can identify intent #18, #8, #12, #2, and #11 in descending order. From the samples of each intent, we find the #intent #18 and #8 are closely related to the food cooking scenarios when #11 contains some food storage scenarios. The #12 and #2 are more likely to focus on the room scenarios. We also observe that there are some computer frames in #12 and #2. Previewing the related shot, we notice that the computer is the foreground object of the room, as Fig. 4. C shows. Thus, the snapshot shows that our model successfully captures the food and room scenarios. We can find that there are two types of food scenarios identified, i.e., food cooking and food storage. This finding also shows that our approach can provide finer-grained user intent representation.

5 Discussion

5.1 Limitations

Adaptive Granularity: Though our ablation study prove the necessity of the granularity-scalable method in video summarization, our proposed approach is not memory-efficient with two pathways of fixed granularity. We will design an adaptive way to control the temporal granularity of the video segments with lower space complexity.

More Modalities: Our IntentVizor framework can support the queries of different modalities. However, we only evaluate our approach on textual and visual queries. Our future work will extend our framework to support other queries, e.g., audio, sketch, etc.

Evaluation of the Interface: Despite that our proposed interface can assist users in the video summarization by a case study, the effectiveness of this interface should be also verified by an in-the-wild user study in the future.

5.2 Applications

As our proposed IntentVizor improves the interpretability and interactivity of the video summarization, it also has potential practical value. As the user can control the output of summary adaptively based on their detailed needs, such summarization can widely be used in customer-obsessed video browsing, data transportation/recording, surveillance analysis, and sports game highlights etc.

5.3 Conclusion

In this work, we propose IntentVizor, an interactive video summarization framework guided by the generic query. First, our framework introduces a novel concept “intent”, which originally come from Information Retrieval (IR) community, to represent the multi-modality queries. Second, we develop a prototype to make the proposed framework interactive with the user. The user can control the intent to generate summaries satisfying their needs. Third, for the model part, two novel intent/summary modules are designed to better understand the generic queries and generate summaries accordingly/adaptively. Both quantitative and qualitative experiment results verify the superiority of our proposed approach. Four ablation studies also verify more potential extensibility of the proposed framework. For future work, we will solve the limitation above, and introduce more query modalities to better satisfy users’ video summarization needs.

6 Acknowledgement

Guande Wu was partially supported by an NYU School of Engineering Fellowship. This research is also partially funded by C2SMART, a Tier 1 University Center awarded by U.S. Department of Transportation under contract 69A3351747124, and NSF awards CNS-1229185, CCF-1533564, CNS-1544753, CNS-1730396, and CNS-1828576. Lin, Silva, and Wu are partially funded by DARPA Perceptually-enabled Task Guidance (PTG). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF, USDOT, or DARPA.

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